title: Induced decondensation of heterochromatin in Drosophila melanogaster polytene chromosomes under condition of ectopic expression of the Supressor of underreplication gene.
abstract: Overexpression of Suppressor of Underreplication protein (SUUR) induces giant reversible swellings in intercalary and pericentric heterochromatin of salivary gland polytene chromosomes. Here, we demonstrate that morphology and extent of swellings are highly dependent on the fixation conditions used: upon glutaraldehyde fixation, we observed moderate decondensation of heterochromatic regions, which was significantly more pronounced upon acetic-acid fixation. Swellings are formed in a PARP-independent fashion. Together with data on inactive transcription in them, this indicates that the swelling-forming regions fail to acquire any features of puffs, the regions typically forming locally decondensed chromatin. Large swellings display striking re-localization of histones and SUUR protein, which are now found at the periphery of the swellings, in contrast to the DNA that fills the entirety of the swelling. We show that swelling-embedded DNA is capable of undergoing replication, however SUUR overexpression drastically alters replication timing in salivary gland cells. We speculate that swelling formation results from SUUR tipping the balance against other proteins that contribute to the organization of repressed chromatin regions.
authors: Institute of Chemical Biology and Fundamental Medicine, Novosibirsk, Russia.
authors: Tatyana D
authors: TD
authors: Kolesnikova
authors: Valeriy F
authors: VF
authors: Semeshin
authors: Eugeniya N
authors: EN
authors: Andreyeva
authors: Ivan A
authors: IA
authors: Zykov
authors: Elena B
authors: EB
authors: Kokoza
authors: Darya A
authors: DA
authors: Kalashnikova
authors: Elena S
authors: ES
authors: Belyaeva
authors: Igor F
authors: IF
authors: Zhimulev
mesh_terms: D000818:Animals; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D005404:Fixatives / Q000494:pharmacology*; D006570:Heterochromatin / Q000187:drug effects / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D059007:Polytene Chromosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005404:Fixatives; D006570:Heterochromatin; C464850:SuUR protein, Drosophila; D011065:Poly(ADP-ribose) Polymerases