Question

Explain how HIV, Influenza and SARS-CoV-2 use host ribosomes for viral protein synthesis?

Answer 1

HIV

from the studies, HIV-1 protein synthesis relies on the host cell translation machinery. tRNAs , amino acids, and initiation, Elongation, and termination factors are also support the host cell translation. throughout the replication cycle, there are several mechanisms that maintains the production of viral proteins. the mechanisms include CAP dependent and IRES - driven . there are several cellular and viral cofactors present for the best production of viral protein. DDX3 RNA helicase is the enzyme protein have role in the translation initiation. first there is a translation mechanism happening at cytoplasm . it is done by host protein synthesis machinery. mRNA occurring by scanning through 40s ribosomal subunit that is recruited at cap. 7 methyl guanylic acid is located at 5 ' terminus of mRNA and scan in 5' to 3' direction. eIF2 - GTP is the inititor tRNA and eIF1A, eIF1, eIF3 , eIF4E, eIF4B eIF4A, and  eIF4G are further participating throughout the process. termed Internal ribosome entry site is is promoting the recruitment of 43 S initiation complex in the cap.

Influenza

the mrna of influenza virus carries a short capped oligonucleotide sequence at their 5 ' end derived by "cap snatching mechanism ". at 3 ' end there is poly A tail. eIF4E cap binding factor is not completely necessary for the mRNA translation of influenza virus. eIF4E , eIF4G, and eIF4A helicase together form eIF4F complex. cap binding site is replaced by eIF4E at 5'. the eIF4F complex with eIF4G recruits 40S ribosomal subunit bound to eIF3. By increasing the activity of cap , enhancing the binding to the capped viral mRNA protecting from cap snitching organism. the host cell protein synthesis is shuts off efficiently by the influenza virus. the protein synthesis following the traditional Pathway except some addition of binding factors.

SARS COV 2

large positive strand rna genome is seen in corona virus. it is 5' capped and 3 ' Polyadenylated. corona virus Translation includes cap dependent and ribosomal Frameshifting . translation activate stress Induced Signaling pathways. the translation is occurring in cytoplasm. initiation, elongation, termination and recycling are th steps included. recognition of mrna and assembling of 80 S ribosome is the primary step. as the traditional Translation , ribosome catalysing the formation of peptide bonds. after trna and mrna are translocated next codon is moved to A site. when termination occurring , the ribosome is released . the recycling step include dissociation of ribosome and release of mrna and deacylated trna. at the initiation step, 60 S subunit is paired to 48S complex to form the 80 S ribosome. like other translations , eIF1, eIF1A, eIF3, eIF4A, etc.. complexes are incorporated with the translation of corona virus. eIF2 triggers GTP hydrolysis. eIF5, eIF5B are facilitating the process and also helping for the formation of 80 S complex.