Histone H3 Lysine 36 Methylation Targets the Isw1b Remodeling Complex to Chromatin

Histone H3 lysine 36 methylation is a ubiquitous hallmark of productive transcription elongation. Despite the prevalence of this histone posttranslational modification, however, the downstream functions triggered by this mark are not well understood. In this study, we showed that H3K36methylation promoted the chromatin interaction of the Isw1b chromatin-remodeling com-plex in Saccharomyces cerevisiae. Similar to H3K36 methylation, Isw1b was found at the mid- and 3 = regions of transcribed genes genome wide, and its presence at active genes was dependent on H3K36methylation and the PWWP domain of the Isw1b sub-unit, Ioc4. Moreover, purified Isw1b preferentially interacted with recombinant nucleosomes that were methylated at lysine 36, and this interaction also required the Ioc4 PWWP domain.While H3K36methylation has been shown to regulate the binding of numerous factors, this is the first time that it has been shown to facilitate targeting of a chromatin-remodeling complex. Chromatin, a nucleoprotein structure that packages DNA in alleukaryotes, serves as a barrier to numerous nuclear processes, such as transcription, replication, and DNA repair. Numerous mechanisms exist for alteration of chromatin structure, including histone posttranslational modifications, the incorporation of his-tone variants, and the activity of chromatin-remodeling com-plexes. There aremany examples of these processes functioning in the same pathway, such as histone acetylation, which promote