tailieunhanh - Báo cáo khoa học: Human cyclin B3 mRNA expression during the cell cycle and identification of three novel nonclassical nuclear localization signals

Cyclins form complexes with cyclin-dependent kinases. By controlling activity of the enzymes, cyclins regulate progression through the cell cycle. A- and B-type cyclins were discovered due to their distinct appearance in S and G2 phases and their rapid proteolytic destruction during mitosis. Transition from G2 to mitosis is basically controlled by B-type cyclins. | ềFEBS Journal Human cyclin B3 mRNA expression during the cell cycle and identification of three novel nonclassical nuclear localization signals Katrin Tschop1 Gerd A. Muller1 Jens Grosche2 and Kurt Engeland1 1 Innere Medizin II Max-Burger-Forschungszentrum Universitat Leipzig Germany 2 Paul-Flechsig-Institut fur Hirnforschung Universitat Leipzig Germany Keywords cellcycle cyclin B3 mRNA expression nuclear localization signal Correspondence K. Engeland Innere Medizin II Max-Burger-Forschungszentrum Universitat Leipzig Johannisallee 30 D-04103 Leipzig Germany Fax 49 341 9712209 Tel 49 341 9725900 E-mail engeland@ Received 6 January 2006 accepted 16 February 2006 doi Cyclins form complexes with cyclin-dependent kinases. By controlling activity of the enzymes cyclins regulate progression through the cell cycle. A- and B-type cyclins were discovered due to their distinct appearance in S and G2 phases and their rapid proteolytic destruction during mitosis. Transition from G2 to mitosis is basically controlled by B-type cyclins. In mammals two cyclin B proteins are well characterized cyclin B1 and cyclin B2. Recently a human cyclin B3 gene was described. In contrast to the expression pattern of other B-type cyclins we find cyclin B3 mRNA expressed not only in S and G2 M cells but also in G0 and G1. Human cyclin B3 is expressed in different variants. We show that one isoform remains in the cytoplasm whereas the other variant is translocated to the nucleus. Transport to the nucleus is dependent on three autonomous non-classical nuclear localization signals that where previously not implicated in nuclear translocation. It had been shown that cyclin B3 coimmunoprecipitates with cdk2 but this complex does not exhibit any kinase activity. Furthermore a degradation-resistant version of cyclin B3 can arrest cells in G1 and G2. Taken together with the finding that cyclin B3 mRNA is not only expressed in G2 M but is also .