Sumoylation of the human histone H4 tail inhibits p300-mediated transcription by RNA polymerase II in cellular extracts
Post-translational modification of histone H4 by the small ubiquitin-like modifier (SUMO) protein was associated with gene repression. However, this could not be proven due to the challenge of site-specifically sumoylating H4 in cells. Biochemical crosstalk between SUMO and other histone modifications, such as H4 acetylation and H3 methylation, that are associated with active genes also remains unclear. We addressed these challenges in mechanistic studies using H4 chemically modified at Lys12 by SUMO-3 (H4K12su) that was incorporated into mononucleosomes and chromatinized plasmids. Mononucleosome-based assays revealed that H4K12su inhibits transcription-activating H4 tail acetylation by the histone acetyltransferase p300, and transcription-associated H3K4 methylation by the extended catalytic module of the Set1/COMPASS histone methyltransferase complex. Activator- and p300-dependent in vitro transcription assays with chromatinized plasmids revealed H4K12su inhibits RNA polymerase II-mediated transcription and H4 tail acetylation. Thus, we have uncovered negative biochemical crosstalk with acetylation/methylation and the direct inhibition of RNAPII-mediated transcription by H4K12su.