Final Activity Report Summary - APOPTOTIC CHROMATIN (Investigating the link between histone phosphorylation and yeast 14-3-3 proteins in programmed cell death)
Modifications on histones control important biological processes, such as transcription and apoptosis, through their effects on chromatin structure. Methylation at H3K4 by Set1 is found at the 5' end of active genes and contributes to transcription activation by recruiting chromatin remodelling enzymes. An adjacent arginine residue (H3R2) is also known to be methylated, but its genomic localisation and function in transcription was unknown. We showed that in mammalian cells as well as in yeast, chromatin is asymmetrically dimethylated at H3R2 (H3R2me2a).
Using an antibody specific for H3R2me2a in ChIP-on-Chip analysis we determine the profile of this modification on the entire yeast genome. We find that H3R2me2a is enriched at all yeast heterochromatic loci, at inactive euchromatic genes and at the 3'-end of active genes. In all cases the pattern of H3R2 methylation is mutually exclusive with the presence of trimethylation at H3K4 (H3K4me3).
This inverse correlation reflects the fact that methylation at H3R2 disrupts the ability of the Set1-complex to bind methylated H3K4 via its Spp1 component, resulting in inhibition of Set1-mediated trimethylation. These results indicate that H3R2me2a controls the global distribution of H3K4me3.
In addition, we demonstrated that H3R2 is also monomethylated (H3R2me1) in yeast but that its functional characteristics are distinct from H3R2me2a:
(a) monomethylated H3R2 does not inhibit methylation of H3K4;
(b) it is present throughout the coding region of genes; and
(c) it correlates with active transcription.
Collectively, these results indicate that different H3R2 methylated states have defined roles in gene expression and provide the first mechanistic insight into the function of arginine methylation on chromatin.
Using an antibody specific for H3R2me2a in ChIP-on-Chip analysis we determine the profile of this modification on the entire yeast genome. We find that H3R2me2a is enriched at all yeast heterochromatic loci, at inactive euchromatic genes and at the 3'-end of active genes. In all cases the pattern of H3R2 methylation is mutually exclusive with the presence of trimethylation at H3K4 (H3K4me3).
This inverse correlation reflects the fact that methylation at H3R2 disrupts the ability of the Set1-complex to bind methylated H3K4 via its Spp1 component, resulting in inhibition of Set1-mediated trimethylation. These results indicate that H3R2me2a controls the global distribution of H3K4me3.
In addition, we demonstrated that H3R2 is also monomethylated (H3R2me1) in yeast but that its functional characteristics are distinct from H3R2me2a:
(a) monomethylated H3R2 does not inhibit methylation of H3K4;
(b) it is present throughout the coding region of genes; and
(c) it correlates with active transcription.
Collectively, these results indicate that different H3R2 methylated states have defined roles in gene expression and provide the first mechanistic insight into the function of arginine methylation on chromatin.