Abstract
Histones are substrates of the SUMO (small ubiquitin-like modifier) conjugation pathway. Several reports suggest histone sumoylation affects transcription negatively, but paradoxically, our genome-wide analysis shows the modification concentrated at many active genes. We find that trans-tail regulation of histone-H2B ubiquitylation and H3K4 di-methylation potentiates subsequent histone sumoylation. Consistent with the known control of the Set3 histone deacetylase complex (HDAC) by H3K4 di-methylation, histone sumoylation directly recruits the Set3 complex to both protein-coding and noncoding RNA (ncRNA) genes via a SUMO-interacting motif in the HDAC Cpr1 subunit. The altered gene expression profile caused by reducing histone sumoylation matches well to the profile in cells lacking Set3. Histone H2B sumoylation and the Set3 HDAC coordinately suppress cryptic ncRNA transcription initiation internal to mRNA genes. Our results reveal an elaborate co-transcriptional histone crosstalk pathway involving the consecutive ubiquitylation, methylation, sumoylation and deacetylation of histones, which maintains transcriptional fidelity by suppressing spurious transcription.