Different types of plant chromatin associated with modified histones H3 and H4 and methylated DNA |
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Authors: | Lidiane Feitoza Marcelo Guerra |
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Institution: | 1.Laboratory of Plant Cytogenetics, Department of Botany,Federal University of Pernambuco,Recife,Brazil;2.Laboratório de Citogenética Vegetal, Departamento de Botanica, Centro de Ciências Biológicas,Universidade Federal de Pernambuco,Recife,Brazil |
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Abstract: | Eukaryotic chromosomes are organized into two large and distinct domains, euchromatin and heterochromatin, which are cytologically
characterized by different degrees of chromatin compaction during interphase/prophase and by post-synthesis modifications
of histones and DNA methylation. Typically, heterochromatin remains condensed during the entire cell cycle whereas euchromatin
is decondensed at interphase. However, a fraction of the euchromatin can also remain condensed during interphase and appears
as early condensing prophase chromatin. 5S and 45S rDNA sites and telomere DNA were used to characterize these regions in
metaphase and interphase nuclei. We investigated the chromosomal distribution of modified histones and methylated DNA in the
early and late condensing prophase chromatin of two species with clear differentiation between these domains. Both species,
Costus spiralis and Eleutherine bulbosa, additionally have a small amount of classical heterochromatin detected by CMA/DAPI staining. The distribution of H4 acetylated
at lysine 5 (H4K5ac), H3 phosphorylated at serine 10 (H3S10ph), H3 dimethylated at lysine 4 or 9 (H3K4me2, H3K9me2), and 5-methylcytosine
was compared in metaphase, prophase, and interphase cells by immunostaining with specific antibodies. In both species, the
late condensing prophase chromatin was highly enriched in H4K5ac and H3K4me2 whereas the early condensing chromatin was very
poor in these marks. H3K9me2 was apparently uniformly distributed along the chromosomes whereas the early condensing chromatin
was slightly enriched in 5-methylcytosine. Signals of H3S10ph were restricted to the pericentromeric region of all chromosomes.
Notably, none of these marks distinguished classical heterochromatin from the early condensing euchromatin. It is suggested
that the early condensing chromatin is an intermediate type between classical heterochromatin and euchromatin. |
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