HIV- 1 protease inhibits Cap- and poly(A)-dependent translation upon eIF4GI and PABP cleavage.
A number of viral proteases are able to cleave translation initiation factors leading to the inhibition of cellular translation. This is the case of human immunodeficiency virus type 1 protease (HIV-1 PR), which hydrolyzes eIF4GI and poly(A)-binding protein (PABP). Here, the effect of HIV-1 PR on cellular and viral protein synthesis has been examined using cell-free systems. HIV-1 PR strongly hampers translation of pre-existing capped luc mRNAs, particularly when these mRNAs contain a poly(A) tail. In fact, HIV-1 PR efficiently blocks cap- and poly(A)-dependent translation initiation in HeLa extracts. Addition of exogenous PABP to HIV-1 PR treated extracts partially restores the translation of polyadenylated luc mRNAs, suggesting that PABP cleavage is directly involved in the inhibition of poly(A)-dependent translation. In contrast to these data, PABP cleavage induced by HIV-1 PR has little impact on the translation of polyadenylated encephalomyocarditis virus internal ribosome entry site (IRES)-containing mRNAs. In this case, the loss of poly(A)-dependent translation is compensated by the IRES transactivation provided by eIF4G cleavage. Finally, translation of capped and polyadenylated HIV-1 genomic mRNA takes place in HeLa extracts when eIF4GI and PABP have been cleaved by HIV-1 PR. Together these results suggest that proteolytic cleavage of eIF4GI and PABP by HIV-1 PR blocks cap- and poly(A)-dependent initiation of translation, leading to the inhibition of cellular protein synthesis. However, HIV-1 genomic mRNA can be translated under these conditions, giving rise to the production of Gag polyprotein.
Castelló
Alfredo
A
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco, Spain.
Franco
David
D
Moral-López
Pablo
P
Berlanga
Juan J
JJ
Alvarez
Enrique
E
Wimmer
Eckard
E
Carrasco
Luis
L
D004686:Encephalomyocarditis virus / Q000235:genetics; D039603:Eukaryotic Initiation Factor-4G / Q000378:metabolism*; D015683:Gene Products, gag / Q000737:chemistry; D016333:HIV Protease / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D008156:Luciferases / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011061:Poly A / Q000378:metabolism*; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C113920:EIF4G1 protein, human; D039603:Eukaryotic Initiation Factor-4G; D015683:Gene Products, gag; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D011061:Poly A; D008156:Luciferases; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1