Protein 4.1 R-135 interacts with a novel centrosomal protein (CPAP) which is associated with the gamma-tubulin complex.
Using a yeast two-hybrid system, we isolated a novel human centrosomal protein, CPAP (centrosomal P4.1-associated protein), which specifically interacts with the head domain of the 135-kDa protein 4.1R isoform (4.1R-135). Sequence analysis revealed that the carboxyl terminus of CPAP has 31.3% amino acid identity with human Tcp-10 (a t-complex responder gene product). Interestingly, most of the sequence identity is restricted to two conserved regions. One carries a leucine zipper, which may form a series of heptad repeats involved in coiled-coil formation; the other contains unusual glycine repeats with unknown function. Immunofluorescence analysis revealed that CPAP and gamma-tubulin are localized within the centrosome throughout the cell cycle. CPAP cosediments with gamma-tubulin in sucrose gradients and coimmunoprecipitates with gamma-tubulin, indicating that CPAP is a part of the gamma-tubulin complex. Furthermore, functional analysis revealed that CPAP is localized within the center of microtubule asters and may participate in microtubule nucleation. The formation of microtubule asters was significantly inhibited by anti-CPAP antibody. Together, these observations indicate that CPAP may play an important role in cell division and centrosome function.
Hung
L Y
LY
Institute of Life Science, National Defense Medical College, Academia Sinica, Taipei 115, Taiwan, Republic of China.
Tang
C J
CJ
Tang
T K
TK
D000595:Amino Acid Sequence; D018385:Centrosome / Q000737:chemistry*; D003598:Cytoskeletal Proteins; D003600:Cytosol / Q000737:chemistry; D015723:Gene Library; D006801:Humans; D008565:Membrane Proteins; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D009479:Neuropeptides; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014404:Tubulin / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
C414735:CENPJ protein, human; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D020033:Protein Isoforms; D011506:Proteins; D012333:RNA, Messenger; D014404:Tubulin; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1