Unusual chromatin state in Emphasis Type="Italic"

Authors: Alejandra Badaracco Eduardo Gorab

Publish Date: 2015/10/21

Volume: 23, Issue: 4, Pages: 781-790

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Abstract

Euchromatin and heterochromatin are usually defined by the degree of DNA compaction gene content and combinations of histone and nonhistone proteins More recent studies on protein location have been able to specify a variety of chromatin types thus adding chromatin configurations other than the two basic reference states Chromatin research exploiting nonmodel organisms has the potential to provide novel information related to epigenetic modifications and their impact on chromosome structure and function Polytene chromosomes of Rhynchosciara americana display a particular region within the A9 subsection characterised by lack of DNA compaction as well as an usual polytene banding pattern DNA content in the subsection seems to be low as deduced by DAPI staining Antibodies to H3K4me a conserved epigenetic transcription marker labelled the A9 subsection strongly In contrast transcriptional activity in the region if any seems to be low as inferred by detection of RNA polymerase II and RNA Histone markers related to heterochromatin formation such as H3K9me and H3K27me are underrepresented in the A9 subsection However a chromodomaincontaining sciarid protein was detected in the region displaying levels of fluorescence very close to those observed in pericentric heterochromatin A plasmid microlibrary constructed with microdissected DNA from the A9 subsection was screened for repetitive DNA The proportion of inserts containing repeats was found to be similar to that contained in another microlibrary made with DNA from a single chromosome end of this species The data suggest an unusual “chromatin colour” indicating that high levels of histone markers related to transcription coexist with a significant presence of chromodomaincontaining proteins and the virtual absence of histone modifications observed in heterochromatin formation

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