Identification of a novel resident centrosomal protein

Abstract

One human autoimmune serum was identified to react with centrosomes by immunofluorescence. We applied the affinity purification of membrane-bound antibody technique and demonstrated that the antibodies present in this antiserum reacted with a 31/29 ku centrosomal antigen. Immunofluorescence showed that this antigen is located at centrosome in a cell-cycle independent manner, and thereby it belongs to the family of centrosomal residents. We then utilized this autoimmune serum and antibodies against centrin and gamma-tubulin to investigate changes of centrosome cycle kinetics during premature chromosome condensation (PCC) artificially induced in V79-8 cells. We show here that centrosomal proteins continue to express when cells are synchronized at G1/S boundary and S phase by Hydroxyurea (HU). During this time, the addition of caffeine causes cells with unreplicated genome to go into mitosis, and induces the separation of the replicated centrosomes. These results suggest that the coordination of DNA synthesis and centrosome replication in the normal cell cycle can be uncoupled. Cells ensure that centrosome duplicates once, and only once during each DNA synthesis cycle through the tight and subtle coordination of cell cycle engine molecules, and thereby the assembly of bipolar spindle and the accurate transmission of genetic information.