Elucidation of host-retrovirus interaction by analyzing chromatin dynamics

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For the establishment of new virology after the post-genome era, it is important to elucidate molecular basis of epigenetics and to understand infection mechanisms by analyzing dynamics of host and viral chromatin. The goal of this project is to elucidate molecular mechanisms of early infection, latent infection of retrovirus and lentiviruses through viral transcriptional initiation, maintenance, gene silencing and reactivation, which involves chromatin remodeling factor, SWI/SNF complex. During these three years of this project, we obtained following results.1.We clearly demonstrated that Brm subunit of human SWI/SNF complex is essential for stable and prolonged transcription drived by MLV-LTR or HIV-LTR in the absence of tat. In human tumor cell lines that are deficient in Brm expression, the expression of MLV- or HIV- based vectors are rapidly silenced in a stochastic manner.2.Using proteomics, we have identified several proteins that substoichiometorically interact with SWI/SNF complex. Among them, we scrutinized p54^<nrb>, because this protein is suggested to be involve in transcription, splicing and RNA editing and also because it can bind to a specific region if HIV RNA. Our analysis clearly indicated that p54^<nrb> and SWI/SNF complex translocates several promoter regions and they also bind to the downstream of the promoter or its RNA transcripts, affecting splicing patterns.In Brm deficient cell lines, therefore, some exons were tend to be excluded. We are now analyzing whether p54^<nrb> is also affect the splicing of HIV that produces several subgenomic RNA.