Dysregulation of histone methylation in SV40 chromosomes during replication results in aberrant transcription and chromatin structure.

Since early and late transcription are both regulated from the same central regulatory region in SV40 chromatin, the location of nucleosomes carrying histone modifications may contribute to controlling the direction of transcription from the regulatory region. This could occur through the generation of active chromatin in the direction of transcription and repressive chromatin in the opposite direction. In order to test this hypothesis, we have characterized the products of SV40 transcription and location of nucleosomes carrying histone modifications in SV40 chromatin following treatment of infected cells with inhibitors of histone methylation metabolism. The inhibitors used included GSK-LSD1 to inhibit demethylation of H3K4me1 and H3K9me1, A366 to inhibit the introduction of H3K9me1, and UNC1999 to inhibit the introduction of H3K27me3. The results are consistent with a regulatory model in which nucleosomes carrying H3K9me1 and H3K27me3 located at the ends of the SV40 regulatory region act to regulate transcription.