Which of the following is not a structural gene of HIV?
Correct Answer: Tat
Description: Ans. d (Tat) (Ref. H-17th/114l; Figure 182-5).HIV Genome - Like other retroviruses, HIV-1 has genes that encode the structural proteins of the virus:# gog encodes the proteins that form the core of the virion (including p24 antigen);# pol encodes enzymes responsible for protease processing of viral proteins, reverse transcription, & integration;# env encodes the envelope glycoproteins.HIV-1 is more complex than other retroviruses, in that it also contains at least six other genes (tat, rev, nef vif vpr, and vpu), which code for proteins involved in the modification of the host cell to enhance virus growth and the regulation of viral gene expression. Several of these proteins are thought to play a role in the pathogenesis of HIV disease. Flanking these genes are the long terminal repeats (LTRs), which contain regulatory elements involved in gene expression.The major difference between the genomes of HIV-1 and HIV-2 is the fact that HIV-2 lacks the vpu gene and has a vpx gene not contained in HIV-1.LTR: Long terminal repeat# Contains control regions that bind host transcription factors (NF-kB, NFAT, Sp.l, TBP).# Required for the initiation of transcription# Contains RNA trans-acting response element (TAR) that binds tat.vif: Viral infectivity factor (p23)# Overcomes inhibitory effects of APOBEC, preventing hypermutation and viral DNA degradation.vpu: Viral protein U# Promotes CD4 degradation and influences virion releasenef: Negative effector (p27)# Promotes downregulation of surface CD4 and MHC 1 expression# Blocks apoptosis# Enhances virion infectivity# Alters state of cellular activation# Progression to disease slowed significantly in absence of NE.vpr: Viral protein R (pl5)# Promotes G2 cell-cycle arrest# Facilitates HIV infection of macrophages.rev: Regulator of viral gene expression (pl9)# Binds RRE# Inhibits viral RNA splicing and promotes nuclear export of incompletely spliced viral RNAs.tat: Transcriptional activator (pl4)# Binds TAR# In presence of host cyclin T1 and CDK9 enhances RNA Pol II elongation on the viral DNA template.gag: Pr55gag# Polyprotein processed by PR MA, matrix (pi7)# Undergoes myristylation that helps target gag polyprotein to lipid rafts;# CA, capsid (p24) binds cyclophilin A NC, nucleocapsid (p7) Zn finger, RNA-binding protein p6# Interacts with Vpr; contains late domain (PTAP) that binds TSG101 and participates in terminal stops of virion budding.pol: Polymerase# Encodes a variety of viral enzymes, including PR (plO), RT, and RNAase H (p66/51), and IN (p32) all processed by PR.env: gp 160 envelope protein# Cleaved in endoplasmic reticulum to gpl20 (SU) and gp41 (TM)# gpl20 mediates CD4 and chemokine receptor binding, while gp41 mediates fusion# Contains RNA response element (RRE) that binds Rev.
Category:
Microbiology
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