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PubMed · 10764593

NAP-2: histone chaperone function and phosphorylation state through the cell cycle.

P Rodriguez·J Pelletier·G B Price·M Zannis-Hadjopoulos
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Abstract

We have recently cloned the human nucleosome assembly protein 2 (NAP-2). Here, we demonstrate that casein kinase 2 (CKII) from HeLa cell nuclear extracts interacts with immobilized NAP-II, and phosphorylates both NAP-2 and nucleosome assembly protein 1 (NAP-1) in vitro. Furthermore, NAP-1 and NAP-2 phosphorylation in crude HeLa cell extracts is abolished by heparin, a specific inhibitor of CKII. Addition of core histones can stimulate phosphorylation of NAP-1 and NAP-2 by CKII. NAP-2 is also a phosphoprotein in vivo. The protein is phosphorylated at the G0/G1 boundary but it is not phosphorylated in S-phase. Here, we show that NAP-2 is a histone chaperone throughout the cell cycle and that its cell-cycle distribution might be governed by its phosphorylation status. Phosphorylated NAP-2 remains in the cytoplasm in a complex with histones during the G0/G1 transition, whereas its dephosphorylation triggers its transport into the nucleus, at the G1/S-boundary, with the histone cargo, suggesting that binding to histones does not depend on phosphorylation status. Finally, indirect immunofluorescence shows that NAP-2 is present during metaphase of HeLa and COS cells, and its localization is distinct from metaphase chromosomes.

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AnimalsBiological TransportCasein Kinase IICell CycleCell Cycle ProteinsCell ExtractsCell LineCell NucleusChromatography, AffinityChromosomesCytoplasmEnzyme ActivationG1 PhaseHeLa CellsHeparinHistonesHumansMetaphaseMolecular ChaperonesNuclear ProteinsNucleosome Assembly Protein 1PhosphoproteinsPhosphorylationProtein BindingProtein Serine-Threonine KinasesProteinsS PhaseJournal ArticleResearch Support, Non-U.S. Gov't

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P Rodriguez, J Pelletier, G B Price, M Zannis-Hadjopoulos. 2000-04-28. NAP-2: histone chaperone function and phosphorylation state through the cell cycle.. https://doi.org/10.1006/jmbi.2000.3674

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