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HIV/Retroviruses

Overview of the molecular biology of HIV as an example of retroviruses

QuestionAnswer
What is the viral receptor for HIV? CD4
What are the co-receptors for HIV? -CCR5 (macrophages) -CXCR4 (CD4+ T cells)
Does HIV have a maturation step in its life cycle? Yes
What is contained in the mature viral particle? A capsid containing: -2 copies of the genome covered by a nucleocapsid -Reverse transcriptase -integrase
What are the three main genes of HIV? -Gag -Pol -Env
What does Gag encode? Structural proteins
What does Pol encode? Enzymes including the RT, protease, and integrase
What does Env encode? The receptor ligand
How is the Gag-Pol protein produced? By -1 ribosomal frameshift
Env is in the same reading frame as Gag-Pol. How is Env produced? Alternative splicing
What shape is the capsid? Conical
How are Env and Vpu obtained? Leaky scanning
What is the overall architecture of the HIV promoter region? 5'-U3-R-U5-3'
What is the function of U3? Contains the viral promoter
What is the function of R? Contains the polyA signal
What is the function of U5? Contains the binding sites of transcription factors
What are the steps of the replication cycle ? -Entry -Reverse transcription -Integration -Transcription/translation -Assembly -Budding -Maturation
What are the steps of receptor attachment? -Attachment and CD4 binding -Co-receptor binding -Membrane fusion
What three things must occur for successful HIV entry? -Lipid mixing -Endocytosis -Content mixing
What does HIV use as a primer for the reverse transcription of its genome? A host endogenous tRNA (Lys)
What happens once the RT reaches the 5' end of the RNA template? RNAse H degrades the already reverse transcribed gRNA, creating a 3' overhanging DNA that is complementary to the other end of the RNA
What happens after RNAse H creates a 3' overhang during reverse transcription? The two complementary R sequences base pair and reverse transcription continues.
What section of the gRNA is not degraded and can act as a primer for (+) DNA production? The poly purine tract (PPT)
Where does reverse transcription take place? In the cytosol
What is the pre-integration complex? The proviral DNA in complex with the integrases and other factors that will enable integration
What is the function of LEDGF/p75? To bind to chromatin, putting the PIC in proximity to the chromatin
What is autointegration? When proviral DNA is inserted into itsself
What is the Trans-activation response element (TAR)? A sequence in the proviral DNA that recruits TAT
What is TAT? An endogenous host protein that gives RNAP its processivity and recruits kinases of the CTD
Does HIV use Leaky scanning? Yes. Leaky scanning is used to access a second reading frame to transcribe Env
What is Rev? A protein critical for export of mRNAs out of the nucleus
What is RRE? Rev response element. Sequence in mRNA that binds Rev
What is DLS? Dimer linkage site. Site of dimerization of the genome that is to be packaged in the viral particles.
What is the Psi sequence? A sequence essential for packaging, binds the nucleocapsid
Where are gammaretroviruses found? As endogenous retroviruses in several species including mice and humans
What molecular biology technique do gammaretroviruses use? Suppression of termination
What is an ecotropic retrovirus? A retrovirus that infects only mice cells
What is a xenotropic retrovirus? A retrovirus that infects species other than mice
What is a polytropic retrovirus? A retrovirus that can infect many species, mice included
What is an amphotropic retrovirus? A retrovirus that can infect many species, but uses a different receptor than that of polytropic retroviruses
What receptor do ecotropic retroviruses use? CAT-1
What receptor do xenotropic retroviruses use? XPR1
What receptor do polytropic retroviruses use? XPR1
What receptor do amphotropic retroviruses use? Pit2
What are 3 ways in which retroviruses can cause cancer? -By carrying a viral oncogene -By inserting into and disrupting a gene important for preventing cancer -By disregulating the expression of a proto-oncogene
Created by: mbell133
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