Transcriptional control by chromosome-associated protein phosphatase-1

Tight regulation of gene expression is critical forcells to respond normally to physiological and environmental cues and to allow cell specialization. Reversible phosphorylation of key structural and regulatory proteins, from histones to the transcriptional machinery, is acknowledged to be an important mechanism of regulating spatial and temporal patterns of gene expression. PP1 (protein phosphatase-1), a major class of serine/threonine protein phosphatase, is found at many sites on Drosophila polytene chromosomes where it is involved in controlling gene expression and chromatin structure. PP1 is targeted to different chromosomal loci through interaction with a variety of different regulatory subunits, which modify PH'S activity towards specific substrates. This mini-review gives an overview of known chromosome-associated PP1 complexes, their role in transcriptional control and the prospects for future analysis.