Interaction between HP1alpha and replication proteins in mammalian cells.
HP1 is an essential heterochromatin-associated protein known to play an important role in the organization of heterochromatin as well as in the transcriptional regulation of heterochromatic and euchromatic genes both in repression and activation. Using the yeast two-hybrid system and immunoprecipitation, we report here that murine HP1alpha interacts with the preRC proteins ORC1, ORC2 and CDC6. Immunofluorescence staining and EGFP/DsRed fusion proteins revealed a colocalization of HP1alpha with ORC1, ORC2 and CDC6 in heterochromatin, supporting the notion that ORC and probably CDC6 play an important role in murine HP1alpha function. Besides that, we also observed a colocalization of HP1alpha with gamma-tubulin suggesting a centrosomal localization of HP1alpha in murine cells. To gain insight into HP1alpha function, we applied the RNAi technique. Depletion of HP1alpha leads to a slow down of cell proliferation, an aberrant cell cycle progression as well as to multinucleated cells with insufficiently organized microtubule. These results together indicate that HP1alpha exerts functions in mitosis and cytokinesis.
Auth
Tanja
T
Institute of Genetics, University of Bonn, 53117 Bonn, Germany. tauth@uni-bonn.de
Kunkel
Elisabeth
E
Grummt
Friedrich
F
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018385:Centrosome / Q000737:chemistry; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D048749:Cytokinesis / Q000502:physiology*; D051379:Mice; D008938:Mitosis / Q000502:physiology*; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000378:metabolism; D051738:Origin Recognition Complex / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D014162:Transfection; D014404:Tubulin / Q000032:analysis
C502132:CDC6 protein, mouse; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D009687:Nuclear Proteins; D051738:Origin Recognition Complex; D034741:RNA, Small Interfering; D014404:Tubulin; D000090266:Chromobox Protein Homolog 5