A role for Jhd2 de-methylase in transcription regulation in S.cerevisiae

Histone tails are subjected to several modifications which form a combinatory code which is read and interpreted by a plethora of regulatory protein complexes. Among the various modifications, lysine (K) methylation is particularly interesting, due to its widespread roles in transcriptional regulation, DNA repair and epigenetic inheritance. In S.cerevisiae, Set1 performs K4 di- and tri-methylation which are removed by the hystone de-methylase Jhd2. The protein Not4 has recently been shown to have an important role in regulating histone H3 methylation at higtly transcribed genes by targeting Jhd2 to proteolysis. We found that Not4 preferentially binds to ribosomal protein (RP) genes and increases H3K4 tri-methylation supporting the model in which H3K4 tri-methylation is controlled by Jhd2 proteolysis.We also found evidence of a regulation of Jhd2 expression in function of cell cycle and of growth rate. Jhd2 mRNA and protein abundance increase after diauxic shift and immediately after release from stationary phase. We analyzed the effects of Jhd2 expression on H3K4 methylation and gene expression. We focused in particular on a group of genes which are strongly modulated at the diauxic shift that we found to drammatically increase their H3K4 tri-methylation upon induction by ChIP on chip experiments. These results suggest a regulatory role of Jhd2 in DS-specific genes transcription.