Short Article Methylation of Histone H3 K4 Mediates Association of the Isw1p ATPase with Chromatin

Summary active genes (Ng et al., 2003).To understand how K4 H3 methylation regulates tran- Set1p methylates lysine 4 (K4) of histone H3 and regu- scription, we attempted to identify proteins that bind to lates the expression of many genes in yeast. Here methylated K4 H3 specifically. We found that human we use a biochemical approach to identify a protein, hSNF2H and the yeast homolog Isw1p bind to H3 tails Isw1p, which recognizes chromatin preferentially when efficiently only when K4 is di- or trimethylated. We pro- it is di- and trimethylated at K4 H3. We show that on vide in vivo evidence that Set1p and Isw1p act together certain actively transcribed genes, the Isw1p chroma- to regulate transcription. tin remodeling ATPase requires K4 H3 methylation toassociate with chromatin in vivo. Analysis of one suchgene, MET16 , shows that the enzymatic activities of ResultsSet1p and Isw1p are functionally connected: Set1pmethylationandIsw1pATPasegeneratespecificchro- Isw1p Binds to Methylated K4 H3matin changesat the5 endof thegene, arenecessary