Introduction

Messenger RNA (mRNA) is a type of RNA molecule that plays a central role in the process of gene expression. It serves as an intermediate between the genetic information encoded in DNA and the synthesis of proteins. mRNA molecules carry the genetic instructions from the DNA in the cell nucleus to the ribosomes in the cytoplasm, where protein synthesis occurs.

Function of mRNA The primary function of mRNA is to convey the genetic code from the DNA to the ribosomes, where it serves as a template for protein synthesis. mRNA molecules are transcribed from specific regions of the DNA called genes, which contain the instructions for producing proteins. Once synthesized, mRNA carries these instructions in the form of codons, which are sequences of three nucleotides that specify particular amino acids.

Structure of mRNA mRNA molecules are single-stranded and typically range in length from a few hundred to several thousand nucleotides. They are composed of four types of nucleotides adenine (A), cytosine (C), guanine (G), and uracil (U). Unlike DNA, which contains thymine (T) instead of uracil, mRNA molecules contain uracil in place of thymine.

Processing of mRNA Before mRNA molecules are translated into proteins, they undergo post-transcriptional modifications, including capping, splicing, and polyadenylation. These modifications help stabilize the mRNA, regulate its stability and translation efficiency, and ensure the accurate transmission of genetic information.

Role in Protein Synthesis During protein synthesis, mRNA molecules are translated by ribosomes, which read the sequence of codons in the mRNA and assemble the corresponding amino acids into a polypeptide chain. Each codon specifies a particular amino acid, and the sequence of codons in the mRNA determines the sequence of amino acids in the protein.

Structure and Function

mRNA molecules typically consist of three main regions

• 5' Untranslated Region (UTR) This region is located at the 5' end of the mRNA molecule and contains sequences that are involved in regulating translation initiation and mRNA stability.
• Coding Region (Open Reading Frame) The coding region contains the genetic code that specifies the amino acid sequence of the protein to be synthesized. It is translated into protein by ribosomes during the process of protein synthesis.
• 3' Untranslated Region (UTR) Situated at the 3' end of the mRNA molecule, the 3' UTR contains sequences that influence mRNA stability, localization, and translational efficiency.

The primary function of mRNA is to carry the genetic instructions transcribed from DNA to the ribosomes, where these instructions are decoded and used as a template for protein synthesis. mRNA molecules act as messengers, conveying the genetic information necessary for the synthesis of specific proteins within the cell.

Historical Background

The discovery of mRNA and its role in protein synthesis represents a cornerstone in the field of molecular biology. Seminal contributions from scientists such as François Jacob, Jacques Monod, and Sydney Brenner in the mid-20th century led to the elucidation of the central dogma of molecular biology, which describes the flow of genetic information from DNA to RNA to protein.

Through groundbreaking experiments and observations, these scientists provided evidence for the existence of mRNA as an intermediate molecule between DNA and protein synthesis. Their work laid the foundation for our current understanding of gene expression and the mechanisms underlying protein synthesis, paving the way for further discoveries in molecular biology and biotechnology.

mRNA plays a central role in the translation of genetic information from DNA to protein, and its discovery represents a landmark achievement in molecular biology, shaping our understanding of fundamental biological processes.

Molecular Mechanisms of mRNA Function

Transcription and mRNA Synthesis

• mRNA is transcribed from DNA in the cell nucleus by RNA polymerase enzymes in a process called transcription.
• Transcription involves three main phases
• Initiation RNA polymerase binds to the promoter region of the DNA, forming a transcription initiation complex. This complex unwinds the DNA double helix and initiates RNA synthesis.
• Elongation RNA polymerase synthesizes a complementary RNA strand by adding nucleotides to the growing mRNA chain in a 5' to 3' direction.
• Termination Transcription ends when RNA polymerase reaches a termination signal in the DNA sequence, leading to the release of the mRNA transcript.

mRNA Processing

• Newly synthesized mRNA undergoes post-transcriptional modifications to produce mature mRNA molecules suitable for translation.
• These modifications include
• 5' Capping Addition of a 7-methylguanosine cap at the 5' end of the mRNA, which protects the mRNA from degradation and facilitates translation initiation.
• Splicing Removal of introns (non-coding regions) from the pre-mRNA transcript and joining of exons (coding regions) to produce a mature mRNA transcript.
• Polyadenylation Addition of a polyadenylate (poly-A) tail at the 3' end of the mRNA, which enhances mRNA stability and regulates translation efficiency.

mRNA Transport and Localization

• Mature mRNA molecules are transported from the nucleus to the cytoplasm through nuclear pores, facilitated by RNA-binding proteins and other transport factors.
• In the cytoplasm, mRNA can undergo further processing and localization to specific subcellular regions, where localized protein synthesis occurs.
• mRNA localization is mediated by RNA-binding proteins and cis-acting elements in the mRNA sequence, allowing for spatial regulation of gene expression.

Translation

• Translation is the process of decoding mRNA by ribosomes to synthesize proteins.
• It involves three main phases
• Initiation The small ribosomal subunit binds to the mRNA at the start codon (AUG), followed by the recruitment of the large ribosomal subunit and initiator tRNA.
• Elongation Ribosomes move along the mRNA in a 5' to 3' direction, synthesizing the polypeptide chain by adding amino acids according to the codons on the mRNA.
• Termination Translation ends when a stop codon is reached on the mRNA, causing the ribosome to release the completed polypeptide chain.

The molecular mechanisms of mRNA function involve transcription, mRNA processing, transport, localization, and translation. These processes are tightly regulated and coordinated to ensure accurate gene expression and protein synthesis within cells. Understanding these mechanisms is essential for elucidating cellular processes and developing therapeutic interventions targeting mRNA.

Regulation of Gene Expression by mRNA

• Post-transcriptional Regulation
• mRNA stability is tightly regulated by various factors acting post-transcriptionally. RNA-binding proteins (RBPs) and non-coding RNAs play crucial roles in modulating mRNA stability and translation efficiency.
• RBPs can bind to specific sequences or structures in the mRNA molecule, influencing its stability, localization, and interaction with translation machinery. For example, some RBPs stabilize mRNA by protecting it from degradation, while others promote mRNA decay by recruiting degradation enzymes.
• Non-coding RNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), regulate gene expression post-transcriptionally. miRNAs are small RNA molecules that can bind to complementary sequences in the 3' UTR of target mRNAs, leading to translational repression or mRNA degradation. Similarly, lncRNAs can interact with mRNA molecules to modulate their stability and translation.
• miRNA and RNA Interference
• miRNAs are key players in post-transcriptional gene regulation and function by base-pairing with target mRNA molecules. This interaction occurs primarily through recognition of specific sequences, known as miRNA response elements (MREs), typically located in the 3' UTR of target mRNAs.
• Binding of miRNAs to target mRNAs can lead to repression of translation or degradation of the mRNA, depending on the degree of complementarity and other regulatory factors. This process, known as RNA interference (RNAi), allows miRNAs to fine-tune gene expression by regulating the abundance and activity of specific mRNA transcripts.
• Through the action of miRNAs, cells can dynamically adjust gene expression in response to internal and external cues, playing critical roles in development, differentiation, homeostasis, and disease processes.

Post-transcriptional regulation of gene expression by mRNA involves intricate mechanisms mediated by RNA-binding proteins and non-coding RNAs, particularly miRNAs. These regulatory processes play essential roles in modulating mRNA stability, translation efficiency, and ultimately, protein expression levels, contributing to the complexity and versatility of gene expression regulation in cells.

mRNA in Disease

• mRNA Dysregulation in Cancer
• Aberrant mRNA expression and processing are hallmark features of cancer, contributing to oncogenesis, tumor progression, and metastasis. Dysregulation of mRNA splicing, in particular, has been implicated in the development and progression of various cancers.
• Alternative splicing, a process that generates multiple mRNA isoforms from a single gene, can lead to the production of protein variants with altered functions or activities. Dysregulated splicing events can result in the expression of oncogenic isoforms or the loss of tumor-suppressive isoforms, promoting cancer cell proliferation, survival, and metastasis.
• Role of mRNA in Neurodegenerative Diseases
• Dysfunctional mRNA metabolism is implicated in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS). Aberrant processing, localization, and translation of mRNA molecules contribute to neuronal dysfunction and degeneration in these diseases.
• In Alzheimer's disease, for example, dysregulation of mRNA splicing and translation is observed in neurons, leading to the accumulation of toxic protein aggregates such as amyloid-beta and tau. Similarly, in Parkinson's disease, alterations in mRNA metabolism affect the expression of proteins involved in mitochondrial function, protein degradation, and oxidative stress responses, contributing to neuronal degeneration.
• Therapeutic Implications
• Targeting mRNA dysregulation holds promise for the development of novel diagnostic and therapeutic strategies for cancer and neurodegenerative diseases.
• In cancer, targeting aberrant mRNA splicing or expression profiles may offer opportunities for precision medicine approaches, including the development of mRNA-based diagnostics, prognostics, and targeted therapies. For example, small molecule inhibitors or antisense oligonucleotides (ASOs) targeting splicing factors or oncogenic mRNA isoforms could be used to selectively inhibit cancer cell growth and metastasis.
• In neurodegenerative diseases, interventions aimed at restoring normal mRNA metabolism and protein homeostasis represent potential therapeutic avenues. This includes the development of gene editing strategies, RNA-based therapeutics (such as ASOs or small interfering RNAs), and modulation of mRNA translation or degradation pathways to mitigate disease pathology and slow disease progression.

Dysregulation of mRNA expression and processing plays critical roles in cancer and neurodegenerative diseases, offering opportunities for the development of targeted diagnostic and therapeutic interventions to improve patient outcomes. Understanding the molecular mechanisms underlying mRNA dysregulation in disease pathology is essential for advancing precision medicine approaches and personalized treatment strategies.

• Therapeutics
• Patisiran (Onpattro) - Approved for the treatment of hereditary transthyretin-mediated amyloidosis (hATTR).
• Pembrolizumab (Keytruda) - Approved for the treatment of various cancers, including melanoma, non-small cell lung cancer, and head and neck squamous cell carcinoma.
• Adalimumab (Humira) - Approved for the treatment of autoimmune diseases such as rheumatoid arthritis, psoriasis, and Crohn's disease.
• Rituximab (Rituxan) - Approved for the treatment of non-Hodgkin's lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis, and other autoimmune diseases.
• Tocilizumab (Actemra) - Approved for the treatment of rheumatoid arthritis, juvenile idiopathic arthritis, giant cell arteritis, and cytokine release syndrome associated with CAR T-cell therapy.
• Vaccines
• BNT162b2 (Comirnaty) - Pfizer-BioNTech COVID-19 vaccine.
• mRNA-1273 (Spikevax) - Moderna COVID-19 vaccine.
• ChAdOx1 nCoV-19 (Vaxzevria) - AstraZeneca COVID-19 vaccine.
• Ad26.COV2.S (Johnson & Johnson's Janssen COVID-19 vaccine) - Johnson & Johnson COVID-19 vaccine.
• BBIBP-CorV (Sinopharm COVID-19 vaccine) - Inactivated COVID-19 vaccine developed by Sinopharm.

mRNA Vaccines

Development of mRNA Vaccines mRNA vaccines represent a groundbreaking vaccine platform that delivers synthetic mRNA encoding antigenic proteins into host cells. Once inside the cells, the mRNA instructs the cells to produce the target antigen, eliciting an immune response. The development of mRNA vaccines has been facilitated by advances in mRNA delivery systems, such as lipid nanoparticles (LNPs), and a deeper understanding of immune mechanisms.

COVID-19 Vaccines and Beyond mRNA vaccines have gained significant attention during the COVID-19 pandemic due to their remarkable efficacy and rapid development timelines. Vaccines such as BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) have demonstrated unprecedented levels of protection against SARS-CoV-2, the virus responsible for COVID-19. The success of mRNA vaccines in combating the pandemic has highlighted their potential for pandemic response and as a platform for vaccine development against other infectious diseases.

Advantages and Limitations mRNA vaccines offer several advantages over traditional vaccine platforms. They can be rapidly developed and manufactured once the genetic sequence of the target antigen is known, making them highly adaptable to emerging infectious threats. Additionally, mRNA vaccines offer scalability and the potential for personalized medicine, as they can be tailored to specific antigens or patient populations.

However, challenges remain in the development and deployment of mRNA vaccines. mRNA stability during storage and delivery is a critical consideration, as mRNA molecules are inherently unstable and prone to degradation. Improving mRNA stability and developing effective delivery strategies, such as LNPs, are ongoing areas of research. Furthermore, optimizing mRNA immunogenicity and minimizing potential adverse effects are important considerations for the widespread adoption of mRNA vaccines.

mRNA vaccines represent a promising vaccine platform with unprecedented potential for pandemic response and infectious disease prevention. While they offer significant advantages, addressing remaining challenges in mRNA stability, immunogenicity, and delivery will be crucial for maximizing their impact on global health.

mRNA Therapeutics

mRNA-Based Therapies for Genetic Disorders mRNA therapeutics offer a promising approach for the treatment of genetic diseases by delivering functional mRNA to cells to replace or supplement defective genes. This includes applications such as gene editing, gene silencing (via RNA interference or RNAi), and gene augmentation therapies. In gene editing, mRNA encoding gene-editing tools such as CRISPR-Cas9 can be delivered to target cells to correct disease-causing mutations. Gene silencing therapies involve delivering mRNA encoding small interfering RNAs (siRNAs) or antisense oligonucleotides (ASOs) to downregulate expression of disease-causing genes. Gene augmentation therapies aim to deliver functional copies of genes to compensate for defective or deficient gene expression.

Protein Replacement Therapy mRNA can serve as a platform for protein replacement therapy by delivering mRNA encoding therapeutic proteins directly into cells. This approach offers advantages over traditional protein therapies, including transient expression of the protein of interest and reduced immunogenicity. mRNA-based protein replacement therapy allows for controlled and regulated expression of therapeutic proteins, potentially leading to more effective and safer treatments for a wide range of diseases.

Applications in Regenerative Medicine mRNA-based approaches hold promise for applications in regenerative medicine by promoting tissue regeneration and repair. mRNA molecules can be designed to induce cellular reprogramming, differentiation, and proliferation, thereby facilitating tissue regeneration in various contexts. For example, mRNA encoding transcription factors or growth factors can be delivered to target cells to stimulate their differentiation into specific cell types or enhance their regenerative capacity. Additionally, mRNA-based approaches can be used to transiently express therapeutic factors in a controlled manner, allowing for precise modulation of cellular processes involved in tissue repair and regeneration.

In summary, mRNA therapeutics offer versatile and promising approaches for the treatment of genetic disorders, protein replacement therapy, and regenerative medicine. Continued research and development in this field hold the potential to revolutionize the treatment of a wide range of diseases and disorders, leading to improved patient outcomes and quality of life.

Future Perspectives

Emerging Technologies and Innovations Ongoing research is focused on overcoming current limitations of mRNA technology, including improving mRNA stability, enhancing delivery efficiency, and minimizing off-target effects. Advances in mRNA synthesis, formulation, and delivery systems, such as lipid nanoparticles (LNPs) and other nanoparticle-based carriers, aim to optimize the pharmacokinetics and biodistribution of mRNA therapeutics and vaccines.

Challenges and Opportunities Addressing challenges such as immunogenicity, scalability, and cost-effectiveness will be crucial for the widespread adoption of mRNA-based therapeutics and vaccines. Strategies to mitigate immune responses against mRNA molecules and delivery vehicles, as well as optimizing manufacturing processes for large-scale production, are areas of active investigation.

Future Directions Future research directions in mRNA technology may include the development of personalized mRNA vaccines tailored to individual genetic profiles or disease characteristics. Targeted delivery systems, such as tissue-specific or cell-specific targeting ligands, hold promise for enhancing the efficacy and safety of mRNA therapeutics. Additionally, combination therapies integrating mRNA with other modalities, such as CRISPR-Cas gene editing or traditional small molecule drugs, represent a promising approach for synergistic therapeutic effects.

Conclusion

Summary of Key Findings mRNA plays a central role in gene expression and has emerged as a versatile tool for both basic research and therapeutic applications. Insights into mRNA biology have provided fundamental understanding of disease mechanisms and paved the way for the development of innovative treatments.

Implications for Biology and Medicine Understanding mRNA biology has profound implications for biology and medicine, offering insights into disease mechanisms, cellular processes, and therapeutic interventions. The ability to modulate gene expression using mRNA-based approaches holds great potential for treating a wide range of diseases, including genetic disorders, infectious diseases, and cancer.

Looking Ahead Continued advancements in mRNA research hold promise for revolutionizing healthcare and addressing unmet medical needs. By harnessing the power of mRNA technology, researchers and clinicians can develop innovative therapies with improved efficacy, safety, and patient outcomes. The future of mRNA-based medicine is bright, with exciting possibilities for transforming the landscape of healthcare

Transcription and mRNA Synthesis

Transcription and mRNA synthesis are essential processes in molecular biology, facilitating the conversion of genetic information encoded in DNA into functional RNA molecules. Here, we'll explore these processes in detail

Transcription Transcription is the first step in gene expression, where a segment of DNA is copied into a complementary RNA molecule by an enzyme called RNA polymerase. This process occurs in the nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells. Transcription involves three main stages initiation, elongation, and termination.

• Initiation Transcription initiation begins with the binding of RNA polymerase to specific DNA sequences called promoters. Promoters are typically located upstream of the transcription start site and contain consensus sequences recognized by RNA polymerase and transcription factors. Once bound to the promoter, RNA polymerase unwinds the DNA double helix, forming a transcription bubble where transcription begins.
• Elongation During transcription elongation, RNA polymerase synthesizes a complementary RNA strand using one of the DNA strands (the template strand) as a template. Nucleotide triphosphates (NTPs) are added to the growing RNA molecule in a 5' to 3' direction, complementary to the template DNA strand. As RNA polymerase moves along the DNA template, the transcription bubble elongates, allowing for continuous RNA synthesis.
• Termination Transcription termination marks the end of RNA synthesis and involves the release of the newly synthesized RNA molecule. In prokaryotes, termination can occur through two mechanisms Rho-dependent termination, which requires the Rho protein to dissociate RNA polymerase from the DNA template, and Rho-independent termination, which relies on specific DNA sequences that form hairpin structures in the RNA transcript. In eukaryotes, termination is more complex and involves cleavage and polyadenylation of the pre-mRNA transcript followed by dissociation of RNA polymerase from the DNA template.

mRNA Synthesis

Messenger RNA (mRNA) synthesis is a specific type of transcription that produces RNA molecules encoding protein-coding sequences. These mRNA molecules serve as templates for protein synthesis by ribosomes in the cytoplasm. mRNA synthesis involves additional steps beyond transcription, including mRNA processing and maturation.

• mRNA Processing Newly synthesized mRNA molecules undergo several post-transcriptional modifications to produce mature mRNA transcripts suitable for translation. These modifications include
• 5' Capping Addition of a modified guanosine cap at the 5' end of the mRNA molecule, which protects the mRNA from degradation and facilitates translation initiation.
• Splicing Removal of introns (non-coding sequences) from the pre-mRNA transcript and joining of exons (coding sequences) to produce a mature mRNA molecule. Splicing is catalyzed by the spliceosome, a complex of RNA and protein components.
• 3' Polyadenylation Addition of a polyadenylate (poly-A) tail at the 3' end of the mRNA molecule, which enhances mRNA stability and regulates translation efficiency.
• mRNA Maturation and Export Once processed, mature mRNA molecules are exported from the nucleus to the cytoplasm through nuclear pore complexes. In the cytoplasm, mature mRNA molecules can undergo further regulatory processes, such as localization to specific subcellular compartments or translation repression by microRNAs (miRNAs) and other RNA-binding proteins.

Transcription and mRNA synthesis are fundamental processes that allow cells to express genetic information encoded in DNA as functional RNA molecules. Understanding the molecular mechanisms and regulation of these processes is essential for elucidating gene expression dynamics and their roles in cellular function and disease.

mRNA Processing

mRNA processing is a crucial step in gene expression that converts precursor mRNA (pre-mRNA) transcripts into mature mRNA molecules suitable for translation. This process involves several post-transcriptional modifications that occur in the nucleus of eukaryotic cells. Here's an overview of mRNA processing

• 5' Capping
• Description The 5' cap is a modified guanosine nucleotide added to the 5' end of the pre-mRNA molecule.
• Function The 5' cap serves multiple functions, including protecting the mRNA from degradation by exonucleases, facilitating mRNA export from the nucleus, and enhancing translation initiation. It also provides a binding site for factors involved in mRNA splicing and translation initiation.
• Splicing
• Description Splicing is the process by which introns (non-coding sequences) are removed from pre-mRNA transcripts, and exons (coding sequences) are joined together to form a mature mRNA molecule.
• Spliceosome Splicing is catalyzed by the spliceosome, a large ribonucleoprotein complex composed of small nuclear ribonucleoproteins (snRNPs) and associated proteins. The spliceosome recognizes consensus sequences at the intron-exon boundaries and mediates the excision of introns and ligation of exons.
• Alternative Splicing Alternative splicing is a regulatory mechanism that generates multiple mRNA isoforms from a single gene by including or excluding different exons. This process increases the diversity of the proteome and can regulate gene expression in response to cellular cues.
• 3' Polyadenylation
• Description Polyadenylation involves the addition of a string of adenine nucleotides (the poly-A tail) to the 3' end of the pre-mRNA molecule.
• Polyadenylation Signal Polyadenylation is directed by a specific sequence motif in the pre-mRNA called the polyadenylation signal (AAUAAA), which is recognized by proteins involved in polyadenylation.
• Function The poly-A tail protects the mRNA from degradation, enhances mRNA stability, and facilitates translation initiation. It also plays a role in mRNA export from the nucleus.
• mRNA Export
• Description Once processed, mature mRNA molecules are exported from the nucleus to the cytoplasm through nuclear pore complexes.
• Export Factors mRNA export is mediated by export factors that recognize and bind to specific mRNA features, such as the 5' cap and poly-A tail, and facilitate the transport of mRNA through the nuclear pores.

In summary, mRNA processing is a complex and highly regulated process that converts pre-mRNA transcripts into mature mRNA molecules ready for translation. These post-transcriptional modifications, including 5' capping, splicing, polyadenylation, and mRNA export, are essential for regulating gene expression and ensuring the fidelity and functionality of mRNA molecules in the cell.

Translation

mRNA translation is the process by which the genetic information encoded in mRNA is decoded by ribosomes to synthesize proteins. This essential cellular process occurs in the cytoplasm of eukaryotic cells and involves several key steps

• Initiation
• Formation of the Initiation Complex Translation initiation begins with the binding of the small ribosomal subunit (40S in eukaryotes) to the mRNA molecule. The small subunit, along with initiation factors and initiator tRNA (tRNAi), forms the initiation complex.
• Recognition of the Start Codon The initiation complex scans along the mRNA molecule until it encounters the start codon, typically AUG (encoding methionine). The start codon is recognized by the anticodon of the initiator tRNA.
• Elongation
• Codon Recognition During elongation, the ribosome moves along the mRNA molecule in a 5' to 3' direction. At each codon, the complementary anticodon of the charged tRNA binds to the mRNA codon in the A site of the ribosome.
• Peptide Bond Formation Peptide bond formation occurs between the amino acids carried by adjacent tRNA molecules in the A and P sites of the ribosome. This forms a growing polypeptide chain attached to the tRNA in the P site.
• Translocation After peptide bond formation, the ribosome translocates along the mRNA molecule, moving the newly formed peptidyl-tRNA from the A site to the P site and exposing the next mRNA codon in the A site for tRNA binding. The uncharged tRNA in the P site is then ejected from the ribosome.
• Termination
• Recognition of Stop Codon Translation continues until a stop codon (UAA, UAG, or UGA) is encountered in the mRNA sequence. Stop codons do not code for any amino acids but instead signal the termination of protein synthesis.
• Release Factor Binding When a stop codon is reached, a release factor protein binds to the A site of the ribosome, causing the hydrolysis of the bond between the completed polypeptide chain and the tRNA in the P site.
• Dissociation The ribosome complex dissociates into its subunits, releasing the newly synthesized protein (polypeptide chain) into the cytoplasm. The ribosomal subunits are then free to initiate another round of translation.
• Post-Translational Modifications
• After translation, the newly synthesized polypeptide chain may undergo various post-translational modifications, such as folding, cleavage of signal sequences, addition of functional groups (e.g., phosphorylation, glycosylation), and assembly into multimeric protein complexes.

mRNA translation is a highly coordinated process involving the decoding of mRNA codons by ribosomes and the sequential addition of amino acids to form a polypeptide chain. This process is essential for protein synthesis, which is fundamental to cell function, growth, and development