title: Nuclear import and activity of histone deacetylase in Xenopus oocytes is regulated by phosphorylation.
abstract: Most of the histone deacetylase (HDAC) activity detected in oocytes and early embryos of Xenopus can be accounted for by the presence of a protein complex that contains the maternal HDACm protein. This complex appears to fulfil the conditions required of a 'deposition' histone deacetylase, its primary function being to deacetylate the core histones incorporated into newly-synthesized chromatin during the rapid cell cycles leading up to blastula. A major event in the assembly and accumulation of the HDAC complex is the translocation of the HDACm protein into the germinal vesicle during oogenesis. Here we examine the features of HDACm that are responsible for its nuclear uptake and enzyme activity, identifying the charged C-terminal domain as a target for modification by phosphorylation. Whereas, one phosphorylation site lying within the putative nuclear localization signal, T445, is required for efficient nuclear import of a GST-carboxy-tail fusion, two others, S421 and S423, appear to effect release from the import receptors. Although overexpression of recombinant HDACm in oocytes leads to premature condensation of endogenous chromatin, this effect is abrogated in vivo by mutation of S421A and S423A. Thus, both translocation and activity of HDACm appear to be regulated by specific phosphorylation events. These results have implications for techniques involving the transfer of somatic nuclei into enucleated oocytes.
authors.affiliation: Division of Cell and Molecular Biology, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TS, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Smillie
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Llinas
authors.forename: James T P
authors.initials: JT
authors.lastname: Ryan
authors.forename: Graham D
authors.initials: GD
authors.lastname: Kemp
authors.forename: John
authors.initials: J
authors.lastname: Sommerville
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000037:antagonists & inhibitors / Q000378:metabolism; D002457:Cell Extracts; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D006655:Histone Deacetylases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017354:Point Mutation / Q000235:genetics; D011374:Progesterone / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D012431:Rutin / Q000494:pharmacology; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D014981:Xenopus / Q000378:metabolism*; D028901:alpha Karyopherins / Q000378:metabolism
chemical_list: D002457:Cell Extracts; D002843:Chromatin; D019913:Nuclear Localization Signals; D028901:alpha Karyopherins; D013912:Threonine; D012694:Serine; D011374:Progesterone; D004004:Dichlororibofuranosylbenzimidazole; D012431:Rutin; D047390:Casein Kinase II; D006655:Histone Deacetylases