The SU(VAR)3-9/HP1 complex differentially regulates the compaction state and degree of underreplication of X chromosome pericentric heterochromatin in Drosophila melanogaster

Olga V. Demakova, Galina V. Pokholkova, Tatyana D. Kolesnikova, Sergey A. Demakov, Eugenia N. Andreyeva, Elena S. Belyaeva, Igor F. Zhimulev

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

In polytene chromosomes of Drosophila melanogaster, regions of pericentric heterochromatin coalesce to form a compact chromocenter and are highly underreplicated. Focusing on study of X chromosome heterochromatin, we demonstrate that loss of either SU(VAR)3-9 histone methyltransferase activity or HP1 protein differentially affects the compaction of different pericentric regions. Using a set of inversions breaking X chromosome heterochromatin in the background of the Su(var)3-9 mutations, we show that distal heterochromatin (blocks h26-h29) is the only one within the chromocenter to form a big "puff"-like structure. The "puffed" heterochromatin has not only unique morphology but also very special protein composition as well: (i) it does not bind proteins specific for active chromatin and should therefore be referred to as a pseudopuff and (ii) it strongly associates with heterochromatin-specific proteins SU(VAR)3-7 and SUUR, despite the fact that HP1 and HP2 are depleted particularly from this polytene structure. The pseudopuff completes replication earlier than when it is compacted as heterochromatin, and under-replication of some DNA sequences within the pseudopuff is strongly suppressed. So, we show that pericentric heterochromatin is heterogeneous in its requirement for SU(VAR)3-9 with respect to the establishment of the condensed state, time of replication, and DNA polytenization.

Original languageEnglish (US)
Pages (from-to)609-620
Number of pages12
JournalGenetics
Volume175
Issue number2
DOIs
StatePublished - Feb 2007

ASJC Scopus subject areas

  • Genetics

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