Applying ChIP-chip analysis to cellular promoter regions, we recently observed that adenovirus small E1A protein (e1a) forces contact-inhibited primary human fibroblasts to enter S-phase by re-localizing RB-family proteins and the major, closely related nuclear lysine acetyl transferases and transcriptional co-activators p300 and CBP on a global scale across the genome. We found that p300 and CBP are primarily responsible for acetylation of histone H3 on lysine 18 (H3K18ac) and that H3K18ac in promoter regions correlates with transcriptional activation. e1a removes RB-family proteins from the promoter regions of genes involved in cell cycle progression, DNA synthesis and cell growth which are induced, and re-localizes them to promoter regions of host cell genes involved in cellular defenses against viral infection which are repressed. In recent unpublished research applying ChIP-seq analysis we found that H3K18ac is broadly removed from the promoter regions of repressed genes and intergenic and intragenic regions and becomes localized primarily to the promoter regions of e1a-induced genes. We found that e1a induced H3K18ac in promoter regions and transcriptional activation primarily of host cell genes associated with the tumor suppressor RB1 and not at host cell genes associated with RB1 paralogs p130 and/or p107 that are not significant tumor suppressors. We propose to further analyze localization of e1a, p300/RB and RB-family proteins across the entire genome using ChIP-seq analysis following expression of e1a. We will explore the mechanisms that target e1a, p300/CBP, and RB-family proteins to specific locations in chromatin, the mechanism of e1a repression of host cell genes involved in anti-viral responses, and e1a activation of viral genes and host cell genes involved in cellular proliferation. This will be done by performing ChIP-seq analysis following expression of e1a mutant in its p300/CBP binding sites and its RB-binding sites and following expression of mutant forms of p300 defective for KAT activity and deleted of its bromo-domain. The proposed studies should yield a deeper understanding of mechanisms that target chromatin-associated proteins to specific genomic locations and functions of p300/CBP and the individual RB-family proteins.
Studies of viruses that can cause cancer in mice, rats and hamsters have taught us about the fundamental cellular abnormalities responsible for many human cancers. We will continue in depth research on how one of these oncogenic viruses, adenovirus 5, forces normally non-dividing cells to grow and divide by rearranging proteins associated with cellular DNA that turn cellular genes on and off.
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