Journal Article DKFZ-2026-02220

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HP1α binding creates a local barrier against transcription activation and persists during chromatin decondensation.

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2026
Cell Press [Cambridge, Mass.]

Molecular cell 86, 3759–3773 () [10.1016/j.molcel.2026.08.013]
 GO

Abstract: Mouse pericentric heterochromatin forms compacted, transcriptionally silent domains, termed chromocenters, that are enriched in heterochromatin protein 1 (HP1). Whether HP1α represses chromocenters by binding locally or by maintaining a phase-separated compartment is unresolved. We investigated this question by recruiting transcriptional activators to mouse fibroblast chromocenters and quantifying repression at a transcription reporter. HP1α established a promoter-proximal barrier that suppressed weaker activators (VP16) but was overcome by stronger ones (VP64-p65-Rta [VPR] and p65). Activator-induced decondensation and transcription occurred without displacing HP1α or H3K9 trimethylation, and HP1α retained its granular distribution and stoichiometric binding dynamics. Multi-color super-resolution imaging revealed spatial segregation of transcribed and HP1α-bound regions at the nanodomain scale. A nanodomain model captured how repeat clusters independently transition between silenced and activated states. These data establish that HP1α and H3K9me3 act through independently switchable nanodomains, accounting for chromocenter regulation without invoking phase separation.

Keyword(s): H3K9me3 ; VP16 ; VPR ; chromatin decondensation ; chromocenter ; dCas9 ; heterochromatin protein 1 ; histone acetylation ; p65 ; transcriptional activation ; transcriptional repression

Classification:

Note: #EA:B066#LA:B066# / 86, 3759–3773

Contributing Institute(s):
  1. Chromatin-Netzwerke (B066)
Research Program(s):
  1. 312 - Funktionelle und strukturelle Genomforschung (POF4-312) (POF4-312)

Appears in the scientific report 2026
Database coverage:
Medline ; BIOSIS Previews ; Biological Abstracts ; Clarivate Analytics Master Journal List ; Current Contents - Life Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 15 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection
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 Record created 2026-09-09, last modified 2026-10-15



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