In vivo HP1 targeting causes large-scale chromatin condensation and enhanced histone lysine methylation.
Changes in chromatin structure are a key aspect in the epigenetic regulation of gene expression. We have used a lac operator array system to visualize by light microscopy the effect of heterochromatin protein 1 (HP1) alpha (HP1alpha) and HP1beta on large-scale chromatin structure in living mammalian cells. The structure of HP1, containing a chromodomain, a chromoshadow domain, and a hinge domain, allows it to bind to a variety of proteins. In vivo targeting of an enhanced green fluorescent protein-tagged HP1-lac repressor fusion to a lac operator-containing, gene-amplified chromosome region causes local condensation of the higher-order chromatin structure, recruitment of the histone methyltransferase SETDB1, and enhanced trimethylation of histone H3 lysine 9. Polycomb group proteins of both the HPC/HPH and the EED/EZH2 complexes, which are involved in the heritable repression of gene activity, are not recruited to the amplified chromosome region by HP1alpha and HP1beta in vivo targeting. HP1alpha targeting causes the recruitment of endogenous HP1beta to the chromatin region and vice versa, indicating a direct interaction between the two HP1 homologous proteins. Our findings indicate that HP1alpha and HP1beta targeting is sufficient to induce heterochromatin formation.
Verschure
Pernette J
PJ
Swammerdam Institute for Life Sciences, BioCentrum Amsterdam, University of Amsterdam, P.O. Box 94062, 1090 GB Amsterdam, The Netherlands. pj.verschure@science.uva.nl
van der Kraan
Ineke
I
de Leeuw
Wim
W
van der Vlag
Johan
J
Carpenter
Anne E
AE
Belmont
Andrew S
AS
van Driel
Roel
R
D002478:Cells, Cultured; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D002877:Chromosomes, Human / Q000378:metabolism; D020868:Gene Silencing; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D006570:Heterochromatin / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D009875:Operator Regions, Genetic; D011496:Protein Methyltransferases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism
C000715593:CBX1 protein, human; C000715594:CBX5 protein, human; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C485184:enhanced green fluorescent protein; D000090266:Chromobox Protein Homolog 5; D049452:Green Fluorescent Proteins; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C454062:SETDB1 protein, human; D008239:Lysine