Discovery of a distinct domain in cyclin A sufficient for centrosomal localization independently of Cdk binding.
Centrosomes have recently emerged as key regulators of the cell cycle. The G1/S transition requires a functional centrosome, and centrosomal localization of numerous proteins, including cyclin/Cdk complexes, is important for the G2/M transition. Here we identify a modular centrosomal localization signal (CLS) localizing cyclin A to centrosomes independently of Cdk binding. The cyclin A CLS is located in a distinct part of the molecule compared with the cyclin E CLS and includes the MRAIL hydrophobic patch involved in substrate recognition. The cyclin A CLS interacts with p27(KIP1), and expression of p27(KIP1) removes cyclin A but not cyclin E from centrosomes. Expression of the cyclin A CLS displaces both endogenous cyclin A and E from centrosomes and inhibits DNA replication, supporting an emerging concept that DNA replication is linked to centrosomal events. Structural analysis indicates that differences in surface charge and length of the C-terminal helix explain why the MRAIL region in cyclin E is not a functional CLS. These results indicate that the cyclin A CLS may contribute to targeting and recognition of centrosomal Cdk substrates and is required for specific effects of p27(KIP1) on cyclin A-Cdk2.
Howard Hughes Medical Institute, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Gaetan
G
Pascreau
Frank
F
Eckerdt
Mair E A
ME
Churchill
James L
JL
Maller
D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D002460:Cell Line; D018385:Centrosome / Q000378:metabolism*; D019925:Cyclin A / Q000737:chemistry* / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*; D014981:Xenopus
D019925:Cyclin A; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases