Flickinger R (2015), AT-rich repetitive DNA sequences, transcription...

XB-ART-53231

Mech Dev 2015 Nov 01;138 Pt 3:227-32. doi: 10.1016/j.mod.2015.10.004.

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AT-rich repetitive DNA sequences, transcription frequency and germ layer determination.

Flickinger R .

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Non-coding sequences of frog embryo endoderm poly (A+) nuclear RNA are AU-enriched, as compared to those of ectoderm and mesoderm. Endoderm blastomeres contain much less H1 histone than is present in ectoderm and mesoderm. H1 histone preferentially binds AT-rich DNA sequences to repress their transcription. The AT-enrichment of non-coding DNA sequences transcribed into poly (A+) nuclear RNA, as well as the low amount of H1 histone, may contribute to the higher transcription frequency of mRNA of endoderm, as compared to that of ectoderm and mesoderm. A greater accumulation of H1 histone in presumptive mesoderm and ectoderm may prevent transcription of endoderm specifying genes in mesoderm and ectoderm. Experimental upregulation of various transcription factors (TFs) can redirect germ layer fate. Most of these TFs bind AT-rich consensus sequences in DNA, suggesting that H1 histone and TFs active during germ layer determination are binding similar sequences.

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Species referenced: Xenopus laevis
GO keywords: DNA binding [+]

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	Fig. 1. Percentage hybridization of nuclear RNA transcribed from repetitive DNA of early neurulae, tailbuds and larvae. RNA was labeled in vitro with H3-dimethylsulfate. RNA samples were incubated with nitrocellulose filters containing 1.24 μg of denatured frog DNA for 48 h at 37 °C in a NaCl–Na citrate-formamide solution.
	Fig. 2. Depletion of 600 μg of H3-dimethylsulfate labeled nuclear RNA transcribed from repetitive DNA of early neurulae, tailbuds and larvae by successive additions of filters containing denatured frog DNA.