New roles of Histone H1 in transcription
Top: Transcriptionally inactive chromatin. Bottom: Transcriptionally active chromatin. Linker histone H1 is an important component of chromatin. The addition of small acetyl groups to H1 regulates transcription.
Genes Dev April 15, 2012
April 15, 2012
Studies led by Robert Schneider team, with those of Stéphane Viville and Laszlo Tora, have brought to light a dual role of histone H1 in transcription activation. Their work is published on April 15th 2012 in Genes & Development.
To store the 2 meters of DNA within the nucleus of a cell, the DNA has to be highly condensed. The linker histone H1 has a key-role for the packing the DNA into a structure called chromatin. The degree of packing can regulate gene expression: if DNA is tightly packed (heterochromatin), genes are not expressed. On the contrary, if chromatin is lightly packed (euchromatin), DNA is then accessible, e.g. to the transcription machinery. Robert Schneider's team, in collaboration with Stéphane Viville's and Laszlo Tora's teams, has shown that, in addition to its structural role, histone H1 is in fact a fine “tuner” of gene-expression. This molecule could turn from a transcriptional repressor into an activator, in particular via the addition of small acetyl groups (called acetylation) to a specific position in its N-terminal tail . They found that histone H1 acetylation can regulate transcription via two mechanisms: the increase of H1 mobility, creating an open accessible chromatin environment and the recruitment of general transcription factors. These results also suggest that H1 acetylation could favor a state as it is found in induced pluripotent stem (iPS) cells and could be involved in germ cell tumors.