Replication serves as a trans‐generational epigenetic switch during SV40 infection (563.2)

Abstract

We have recently shown that the repression of early transcription during a Simian Virus 40 (SV40) infection results in different histone modifications depending upon the replicative status of the chromatin (Kallestad, et al., 2013, Frontiers in Genetics). In order to test whether replication affected other aspects of transcriptional regulation, we have analyzed SV40 chromosomes for the presence of the methylated forms of H3K4 and H3K9 following dysregulation of transcription by DRB which inhibits RNA Polymerase II elongation, and sodium butyrate which increases transcription from genes committed to transcription. SV40 chromosomes from treated and control infections were isolated between 2 and 12 hours post‐infection when only transcription was occurring or 48 hours post‐infection when transcription and replication were both occurring, purified, and subjected to ChIP analyses with antibodies to mono‐, di‐, and tri‐methylated H3K4 and H3K9 followed by real‐time PCR quantitation. Consistent with our previous published results we observed that dysregulation of transcription yielded different epigenetic readouts depending upon whether replication was occurring. Treatment with DRB resulted in a large increase in the levels of H3K9me2 and me3 in the presence of replication but had little effect on the levels of these modfications in the absence of replication. Treatment with sodium butyrate had the opposite effects. There was a significant reduction in H3K9me3 during replication and transcription but not when only transcription occurred. Taken together these results indicate that replication acts as a switch to epigenetically define the chromatin structure of newly replicated chromatin which will become new virus particles. Grant Funding Source: Supported by National Institutes of Health grant AI094441 to B.M.