Journal
BIOCHEMICAL JOURNAL
Volume 346, Issue -, Pages 587-591Publisher
PORTLAND PRESS
DOI: 10.1042/0264-6021:3460587
Keywords
inositides; inositol lipids; NLS; nuclear localization; PIPkin
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Type II phosphatidylinositol phosphate kinases (PIPkins) have recently been found to be primarily phosphatidylinositol 5-phosphate 4-kinases, and their physiological role remains unclear. We have previously shown that a Type II PIPkin [isoform(s) unknown], is localized partly in the nucleus [Divecha, Rhee, Letcher and Irvine(1993) Biochem. J. 289, 617-620], and here we show, by transfection of HeLa cells with green-fluorescent-protein-tagged Type II PIPkins, that this is likely to be the Type II beta isoform. Type II beta PIPkin has no obvious nuclear localization sequence, and a detailed analysis of the localization of chimaeras and mutants of the alpha (cytosolic) and beta PIPkins shows that the nuclear localization requires the presence of a 17-amino-acid length of alpha-helix (alpha-helix 7) that is specific to. the beta isoform, and that this helix must be present in its entirety, with a precise orientation. This resembles the nuclear targeting of the HIV protein Vpr, and Type II beta PIPkin is apparently therefore the first example of a eukaryotic protein that uses the same mechanism.
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