Human immunodeficiency virus viral genome

Currently, transcription of the human immunodeficiency virus (HIV) genome by RNA polymerase II provides the best-understood example of regulated transcription termination in eukaryotes. Efficient expression of HIV genes requires a small viral protein encoded at the tat locus. Cells infected... 

Human immunodeficiency virus (HIV) is a retrovirus, i.e. its RNA is converted in human cells by the en me reverse transcriptase to DNA which is incorporated into the human genome and is responsible for producing new HIV particles. Zidovudine (azidothymidine, AZT Fig. 5.22F) is a stmctural analogue of thymidine (Fig. 5.22A) and is used to treat AIDS patients. Zidovudine is converted in both infected and uninfected cells to the mono-, di- and eventually triphosphate derivatives. Zidovudine triphosphate, the aetive form, is a potent inhibitor of HIV replication, being mistaken for thymidine by reverse transeriptase. Premature ehain termination of viral DNA ensues. However, AZT is relatively toxic because, as pointed out above, it is converted to the triphosphate by eellular enzymes and is thus also aetivated in uninfected cells. 

Replication of the human immunodeficiency virus (mV), the causative agent of AIDS, is susceptible to targeted interventions, because several virus-specific metabolic steps occur in infected cells (A). Viral RNA must first be transcribed into DNA, a step catalyzed by viral reverse transcriptase." Double-stranded DNA is incorporated into the host genome with the help of viral inte-grase. Under control by viral DNA, viral replication can then be initiated, with synthesis of viral RNA and proteins (including enzymes such as reverse transcriptase and integrase, and structural proteins such as the matrix protein lining the inside of the viral envelope). 

Human immunodeficiency virus (HIV) is a member of the retrovirus family, classified under the lentivirus genus. Retroviruses are enveloped RNA viruses, which contain a core of capsid proteins, viral RNA, and enzymes. All infectious retroviral virions contain an enzyme, reverse transcriptase, which catalyzes the formation of a complementary DNA strand from an RNA template. A double-stranded DNA copy of the viral RNA genome (proviral DNA) may then be integrated into and replicated with the host cell genome. 

Despite the diversity in the structures of viruses and the types of host cell that are infected, there are several basic steps in the life cycle of all viruses infection (penetration of the virion or its nucleic acid into the host cell), replication (expression of the viral genome), maturation (assembly of viral components into virions), and release (the emission of new virions from the host cell). Because viruses usually possess only enough genetic information to specify the synthesis of their own components, each type must exploit some of the normal metabolic reactions of its host cell to complete the life cycle. For this reason there are numerous variations on these basic steps. This point can be illustrated by comparing the life cycles of two well-researched viruses the T4 bacteriophage and the human immunodeficiency virus (HIV). 

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