A Conserved Sequence Motif in Polycomb-Response Elements

Maintenance of the individual patterns of gene expression in different cell types is required for the differentiation and development of multicellular organisms. Expression of many genes is controlled by Polycomb (PcG) and Trithorax (TrxG) group proteins that act through association with chromatin. PcG/TrxG are assembled on the DNA sequences termed PREs (Polycomb Response Elements), the activity of which can be modulated and switched from repression to activation. In this study, we analyzed the influence of transcriptional read-through on PRE activity switch mediated by the yeast activator GAL4. We show that a transcription terminator inserted between the promoter and PRE doesnt prevent switching of PRE activity from repression to activation. We demonstrate that, independently of PRE orientation, high levels of transcription fail to dislodge PcG/TrxG proteins from PRE in the absence of a terminator. Thus, transcription is not the main factor required for PRE activity switch.

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Faculty Opinions recommendation of Polycomb response elements mediate the formation of chromosome higher-order structures in the bithorax complex.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1091102.546934 ◽

2007 ◽

Author(s):

Leonie Ringrose

Keyword(s):

Higher Order ◽

Bithorax Complex ◽

Response Elements ◽

Polycomb Response Elements ◽

Order Structures

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The Crystal Structure of Shikimate Dehydrogenase (AroE) Reveals a Unique NADPH Binding Mode

Journal of Bacteriology ◽

10.1128/jb.185.14.4144-4151.2003 ◽

2003 ◽

Vol 185 (14) ◽

pp. 4144-4151 ◽

Cited By ~ 32

Author(s):

Sheng Ye ◽

Frank von Delft ◽

Alexei Brooun ◽

Mark W. Knuth ◽

Ronald V. Swanson ◽

...

Keyword(s):

Catalytic Domain ◽

Binding Pocket ◽

Binding Mode ◽

Sequence Motif ◽

Binary Complex ◽

Shikimate Dehydrogenase ◽

Conserved Residues ◽

Conserved Sequence ◽

Nicotinamide Mononucleotide ◽

Reversible Reduction

ABSTRACT Shikimate dehydrogenase catalyzes the NADPH-dependent reversible reduction of 3-dehydroshikimate to shikimate. We report the first X-ray structure of shikimate dehydrogenase from Haemophilus influenzae to 2.4-Å resolution and its complex with NADPH to 1.95-Å resolution. The molecule contains two domains, a catalytic domain with a novel open twisted α/β motif and an NADPH binding domain with a typical Rossmann fold. The enzyme contains a unique glycine-rich P-loop with a conserved sequence motif, GAGGXX, that results in NADPH adopting a nonstandard binding mode with the nicotinamide and ribose moieties disordered in the binary complex. A deep pocket with a narrow entrance between the two domains, containing strictly conserved residues primarily contributed by the catalytic domain, is identified as a potential 3-dehydroshikimate binding pocket. The flexibility of the nicotinamide mononucleotide portion of NADPH may be necessary for the substrate 3-dehydroshikimate to enter the pocket and for the release of the product shikimate.

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