Replication and transcription of SV40 direct distinct epigenetic signaling

Abstract

We have characterized how transcriptional regulatory sequences direct histone modifications during replication and transcription of Simian Virus 40. The role of DNA replication in directing histone modification was determined by analyzing the introduction of histone modifications (H3K4me1,me2,me3 and H3K9me1,me2,me3) from 24 hours to 48 hours post‐infection and following aphidicolin inhibition of DNA replication. Notably, only the introduction of H3K9me1 and H3K4me1 appeared to be totally dependent upon DNA replication. Since the repressive regulatory sequence, Site I, results in the introduction of H3K9me1 during replication, we determined its effect on transcriptional repression early in infection. Consistent with repression, we observed a reduction in SV40 minichromosomes containing RNA polymerase II from 2 hours to 8 hours post‐infection. Unexpectedly, we also observed a reduction in the presence of H3K9me1, H3K9me2, and H3K9me3 indicating that these modifications were not being introduced along with repression. We also analyzed SV40 recombinants containing either one or two copies of Site I and confirmed that the introduction of H3K9me1 was only associated with Site I during replication. Taken together these results indicate that transcriptional regulatory sequences can alter the epigenetic profile of a gene depending upon whether they function during replication or transcription.