Viral DNA integration

Kotin, R. M., Menninger, J. C., Ward, D. C. and Bems, K. I. (1991). Mapping and direct visualization of a region-specific viral DNA integration site on chromosome 19ql3-qter. Genomics 10, 831-834. 

A multinuclear-activation galactosidase indicator (MAGI) infectivity assay was then used to determine the inhibitory stage of bevirimat. It was realised that bevirimat blocks virus replication at a time point after the completion of viral DNA integration and Tat expression.15 Furthermore, several assays, including quantitative radioimmunoprecipitation analysis, demonstrated that bevirimat does not affect virus particle release. 

The preliminary mechanism of action studies indicated that DCK inhibits HIV after viral entry but before viral DNA integration. To further elucidate the mechanism... 

HIV integrase consists of three distinct domains. The N-terminal domain contains a HHCC motif that coordinates a zinc atom that is required for viral cDNA integration. Three highly conserved amino acids (D,D-35-E) are embedded in the core domain, which form the acidic catalytic triad coordinating one or possibly two divalent metals (Mn + or Mg +). The C-terminal domain (residues 213-288) is responsible for unspecific DNA binding and adopts an overall SH3 fold (Chiu and Davies 2004). The enzyme functions as a multimer and to this end all three domains can form homodimers. 

The integration of newly synthesized viral DNA into the host chromosome is a multi-step process (Anthony 2004 Van Made and Debyser 2005) that relies on the integrity of the last 10-20 base pairs at both ends of the viral cDNA besides a fully functional integrase (see Fig. 1). Initially, integrase recogiuzes the long-terminal repeat (LTR) of the retro-transcribed viral DNA and performs endonucleolytic... 

Second, the INSTl, but not an RTl, may conceivably inhibit the virus production from the pool of resting CD4 T cells that are in a state of pre-integration latency (Murray et al. 2007). Upon activation, the preformed pro-viral DNA that is already located in the nucleus integrates into the genome of these cells, allowing them to contribute to the viral load. 

Integration of the various fragments generated into cloning vectors, which are themselves small DNA molecules capable of self-replication. Typically, these are plasmids or viral DNAs and the composite or engineered DNA molecules generated are called rDNA. 

Viral DNA is integrated into the chromosomal DNA of male and female wasps. The virus also exists in an episomal form in female tissues and even in male wasps, though to a much reduced level (4). It is not known whether the linear or the episomal forms of the virus are the templates for viral replication. 

The enzyme reverse transcriptase, as well as some other enzymes used in virus replication the gene that codes these enzymes is the pol gene. The other viral enzymes specified by the pol gene are protease and integrase. Protease is involved in muturation of viral proteins as the virus buds out from the cell, and integrase is responsible for integration of the viral DNA into the cell s chromosomal DNA. 

Once integrated into the host chromosome, the assembly of new viral particles necessitates the prodnction of viral RNA transcripts and proteins. Initiation of viral transcription is also an RNA independent process where host transcription promoters and enhancer elements such as NF-kB bind to the 5 -LTR. The host transcriptional complex is then recrnited and transcription commences.Once transcription has been initiated, RNA and RNA-RNA interactions play a critical role in mediating the production of viral transcripts. The multiprotein transcription complex has a recognition factor for nonhost DNA and quickly releases from viral DNA, creating short, abortive transcripts. Processing and nuclear export of these transcripts leads to the translation of the HIV Tat protein, a small early-phase viral protein (Figure 10.4) that plays a key role in the ultimate formation of fnll-length viral RNA transcripts. 

The end result of integration is the incorporation of the viral DNA into the DNA of the host cell. Once there, the provirus can serve as a template for the production of mRNA, allowing for the synthesis of viral proteins. These are assembled at the cell membrane to produce new viral particles, which then bud off to seek out new cells to infect. The integrated viral DNA is also necessarily copied whenever the host cell undergoes cell division. The insidious nature of... 

It has been demonstrated that the chemical steps that comprise DNA integration are carried out by the viral protein, integrase (IN). Integrase is encoded by the 3 end of the viral pol gene, which also codes for two other viral enzymes, the protease and reverse transcriptase. These three enzymes are initially synthesized as part of a larger polyprotein that is subsequently cleaved by the protease to the individual proteins. 

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