Identification of heterochromatin protein 1 (HP1) as a phosphorylation target by Pim-1 kinase and the effect of phosphorylation on the transcriptional repression function of HP1(1).
Pim-1, a protooncogene product, is a serine/threonine kinase and is thought to play a role in signal transduction in blood cells. Few phosphorylated target proteins for Pim-1, however, have been identified. In the present study, two-hybrid screening to clone cDNAs encoding proteins binding to Pim-1 was carried out, and a cDNA for heterochromatin protein 1gamma (HP1gamma) was obtained. Binding assays both in yeast and in vitro pull-down using the purified HP1gamma and Pim-1 expressed in Escherichia coli showed that Pim-1 directly bound to the chromo shadow domain of HP1gamma. HP1gamma was also associated with Pim-1 in human HeLa cells and the serine clusters located at the center of HP1gamma were phosphorylated by Pim-1 in vitro. Furthermore, a transcription repression activity of HP1gamma was further stimulated by the deletion of the serine clusters targeted by Pim-1. These results suggest that Pim-1 affects the structure or silencing of chromatin by phosphorylating HP1.
Koike
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Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12, Nishi 6, Kita-ku, Sapporo, Japan.
Maita
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Taira
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Ariga
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Iguchi-Ariga
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SM
D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051573:Proto-Oncogene Proteins c-pim-1; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion / Q000235:genetics; D012694:Serine / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection; D020798:Two-Hybrid System Techniques
D002868:Chromosomal Proteins, Non-Histone; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D000090266:Chromobox Protein Homolog 5; D012694:Serine; C496634:PIM1 protein, human; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1