Biochemical characterization of the yeast set1 complex

Abstract

Histone H3 Lysine 4 (H3K4) methylation, a modification that broadly modulates DNA based processes including transcription, is highly conserved in eukaryotes and directly stimulated by monoubiquitylation of histone H2B (H2Bub). Past studies have shown distinct mechanisms involved in H2Bub-dependent H3K4 methylation mediated by the yeast Set1 complex (Set1C) which is the sole enzyme for all H3K4 methylation in yeast. Here, I report the characterization of Set1C components including domains within Spp1, a multi-functional subunit of Set1C. The PHDL of Spp1 mediates the interaction between the n-SET domain of Set1 and the catalytic core subunits to modulate H2Bub-dependent H3K4 methylation. A novel interaction is identified between the N-terminal region of Set1 and Swd1 that compensates the stimulatory activity of Spp1 in context of the full-length Set1C. In addition, I show a direct interaction between Set1C and RNA mediated by the central region of Set1 and their role in chromatin association of Set1C. This study provides a fundamental understanding of the functional relationship between the confirmation and enzyme activity of Set1C and suggests a novel regulatory model to explain H2Bub-dependent H3K4 methylation.