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HP1 binding to native chromatin in vitro is determined by the hinge region and not by the chromodomain
Author(s) -
Meehan Richard R.,
Kao ChengFu,
Pennings Sari
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg306
Subject(s) - chromodomain , biology , chromatin , in vitro , hinge , heterochromatin protein 1 , genetics , microbiology and biotechnology , dna , heterochromatin , physics , gene , helicase , rna , classical mechanics
We have isolated the complete coding sequences for two Xenopus laevis isoforms of heterochromatin protein 1, corresponding to HP1α and HP1γ. The sequence of x HP1α shows considerable divergence from its mammalian homologues, whereas x HP1γ is highly conserved. Functionally, x HP1α behaves identically to human HP1α. We observe unexpected differences between the two HP1 variants in binding native soluble chromatin, which seem to correlate with their distinct nuclear distributions in vivo . A surprising finding is that the characteristic interaction of HP1 chromodomains with histone H3 at methylated lysine 9 is not detected in preformed chromatin due to its inaccessibility. Instead, we localize a strong chromatin‐binding activity to the short hinge region between the chromodomain and the chromoshadow domain of x HP1α but not x HP1γ. This novel chromatin‐binding activity has a non‐specific DNA‐binding component in addition to a linker histone‐dependent preference for an altered chromatin structure with a likely heterochromatin organization.