Histone deacetylases: complex transducers of nuclear signals

Histone acetylation influences both gene transcription and chromatin assemb ly after DNA replication and the enzymes that regulate this properly of chr omatin are likely to play a Key rob in regulating these crucial genomic fun ctions. The steady-state level of histone acetylation is established and ma intained by multiple histone acetyltransferases (HATs) and deacetylases (HD ACs). Both groups of enzymes contain numerous family members, most of which have been highly conserved through evolution. The HDACs have been implicat ed in repression of gene expression by facilitating chromatin condensation and, like the HATs, operate as part Of multi-protein complexes. The non-cat alytic components of these complexes can either target the catalytic subuni t to specific sites on the genome or regulate its enzymatic specificity. Ki nase and phosphatase activities of intracellular signal transduction pathwa ys may modify components of these complexes and thereby regulate their asse mbly, targeting or enzymatic function. (C) 1999 Academic Press.