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Dynamic Histone H1 Isotype 4
Methylation and Demethylation by Histone Lysine
Methyltransferase G9a/KMT1C and the Jumonji
Domain-containing JMJD2/KDM4 Proteins
Abstract
The linker histone H1 generally participates in the
establishment of chromatin structure. However, of
the seven somatic H1 isotypes in humans some are
also implicated in the regulation of local gene
expression. Histone H1 isotype 4 (H1.4) represses
transcription, and its lysine residue 26 (Lys26) was
found to be important in this aspect. H1.4K26 is
known to be methylated and acetylated in vivo, but
the enzymes responsible for these post-translational
modifications and the regulatory cues that promote
H1.4 residence on chromatin are poorly
characterized. Here we report that the euchromatic
histone lysine methyltransferase G9a/KMT1C mediates
H1.4K26 mono- and dimethylation in vitro and in vivo
and thereby provides a recognition surface for the
chromatin-binding proteins HP1 and L3MBTL1.
Moreover, we show evidence that G9a promotes H1
deposition and is required for retention of H1 on
chromatin. We also identify members of the
JMJD2/KDM4 subfamily of jumonji-C type histone
demethylases as being responsible for the removal of
H1.4K26 methylation.
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