Conventional and unconventional mechanisms for capping viral mRNA

Area of Science:

• Molecular Biology
• Virology
• Immunology

Background:

• Messenger RNA (mRNA) 5' end capping is crucial for eukaryotic gene expression, including translation, splicing, nuclear export, and degradation prevention.
• Viruses employ diverse strategies to cap their RNA, often mimicking cellular mRNA caps to evade host defenses and ensure viral replication.
• These viral RNA caps can be acquired from host cells or synthesized via unique viral or host-dependent capping machinery.

Purpose of the Study:

• To review and synthesize the various strategies utilized by viruses to generate functional mRNA 5'-caps.
• To elucidate how viral RNA capping mechanisms contribute to the evasion of innate immune recognition.
• To highlight the diversity in organization, structure, and mechanism of viral capping apparatuses.

Main Methods:

• Comprehensive literature review of viral RNA capping strategies.
• Analysis of molecular mechanisms underlying viral cap synthesis and acquisition.
• Examination of the interplay between viral capping and host innate immunity.

Main Results:

• Viruses utilize distinct methods, including cap-snatching and de novo synthesis, to produce 5'-terminal cap structures on their RNA.
• Viral caps are often indistinguishable from cellular mRNA caps, facilitating viral RNA translation and stability.
• Diverse viral capping apparatuses, varying in complexity and components, have evolved across different viral families.

Conclusions:

• Viral RNA 5' capping is a critical adaptation for efficient viral gene expression and replication within eukaryotic hosts.
• Understanding viral capping strategies provides insights into host-pathogen interactions and innate immune evasion mechanisms.
• The diversity of viral capping mechanisms underscores the evolutionary adaptability of viruses.