First published online November 21, 2008
Development 135, 2405e (2008)
© The Company of Biologists Limited
Pho-nomenal transcriptional memory
During Drosophila development, Polycomb (PcG) and trithorax (trxG)
group proteins maintain DNA regions in transcriptionally silent and active
states, respectively, by forming complexes that modify chromatin.
Surprisingly, Fujioka and colleagues now report that the DNA-binding PcG
protein Pleiohomeotic (Pho) maintains both active and repressed
transcriptional states of even skipped (eve; a
Drosophila gene with a conserved role in the regulation of nervous
system gene expression) through a single site (see
p. 4131). The
researchers identify a Pho-dependent sequence at the 3' border of the
eve locus. They then show that, while this element maintains
repression in nervous system cells in which eve is silenced during
early development, it unexpectedly maintains an active transcriptional state
in other cells. Both negative and positive transcriptional maintenance depend
on Pho binding and on pho gene activity. From these and other
results, the researchers suggest that the differential regulation of a core
DNA-binding complex that contains Pho and other factors facilitates the
transcriptional memory of both active and repressed states during
development.

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Related articles in Development:
- The DNA-binding Polycomb-group protein Pleiohomeotic maintains both active and repressed transcriptional states through a single site
- Miki Fujioka, Galina L. Yusibova, Jian Zhou, and James B. Jaynes
Development 2008 135: 4131-4139.
[Abstract]
[Full Text]