Histone trimethylation and the maintenance of transcriptional on and off states by trxG and PcG proteins

Article Abstract:

The chromatin of HOX gene Ultrabithorax (Ubx) in [Ubx.sup.OFF] and [Ubx.sup.ON] cells purified from developing Drosophila is analyzed to study the molecular basis of polycomb group (PcG) and trithorax group /(trxG) control. The results propose that polycomb response element-tethered PcG protein complexes act over long distances to generate Pc-repressed chromatin that is trimethylated at H3-K27, H3-K9, and H4-K20, but that trxG HMTase Ash1 selectively prevents trimethylation in promoter and coding region in the ON state.

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Drosophila GAGA factor directs histone H3.3 replacement that prevents the heterochromatin spreading

Article Abstract:

A study to show that the Drosophila GAGA factor-FACT complex and its binding site, which downstream from the white gene are crucial fro, position effect variegation was conducted. The findings suggest that the GAGA factor and FACT-dependent replacement of Lys 9-methylated histone H3 by H3.3 counteracts the spreading of silent chromatin.

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Histone variants: deviants?

Article Abstract:

An overview of how the histone variants could result in the changes in chromatin structure and facilitate various specific functions is presented. The information on histone variant assembly into chromatin, the structure of variant chromatin and post-translational modifications that take place on the variants is also presented.

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