| Here , we report the identification of a functional human homolog , hBRE 1 , of the yeast BRE 1 E3 ubiquitin ligase . hBRE 1 specifically increases the global level of H2B ubiquitylation at lysine 120 and enhances activator dependent transcription . ^^^ Moreover , reduction of hBRE 1 by RNAi decreases endogenous H2B ubiquitylation , activator dependent transcription , and interestingly , H 3 K4 and K 79 methylation . ^^^ These studies suggest that hBRE 1 is an H2B specific E 3 ubiquitin ligase and that it functions , through direct activator interactions , as a transcriptional coactivator . ^^^ |