Development of new types of retrovirus vectors that modulate epigenetical regulation.

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In this project, we have designed, prepared and improved several retrovirus/lentivirus vectors that carry efficient transcriptional units for the expression of short hairpin (sh) RNA, miRNA, and the newly developed RNA decoy molecule that inhibits specific miRNA (TuD RNA). Using these vector systems, we have studied cancer epigenetics by concentrating on SWI/SNF chromatin remodeling complex.We have noticed that in human tumor cell lines that are deficient in Brm expression, expression of MLV and HIV vectors that were exogenously transduced into them are rapidly silenced stochastically. We finally demonstrated that Brm-type SWI/SNF complex is essential for the stable expression of retro/lentivirus.Brm is further shown to have antioncogenic potential because exogenous introduction of Brm reduces oncogenic potential of cell lines deficient in Brm expression. In all these cell lines examined, the functional Brm gene is present and is actively transcribed; Brm expression was suppressed at t … More he post-transcriptional level. We hypothesized that Brm is targeted by certain miRNAs and screened several miRNA candidates and finally have shown that miR-199a target Brm mRNA. Interestingly, all the cancer cell lines deficient in Brm have high levels of miR-199a, whereas in Brm expressing cells, miR-199a was marginally expressed.We further show these distinct expression patterns are resulted from double-negativefeedback regulation formed between Brm and miR-199a-5p/-3p via a transcription factor Egr1. We additionally have shown that miR-21 and its target NFIB, a negative transcriptional regulator, also forms a robust feedback regulation in cancer cell lines.We have also shown human requiem protein functions as an adaptor protein that links SWI/SNF complex and RelB/p52. We further showed that introduction of shRNA against REQ strongly suppresses anchourage-independent growth, but does not affect growth in monolayer culture at all in tumor cell lines such as Panc-1, in which non-canonical NFκB pathway is constitutively activated. Less