Open AccessProtein 4.1 R-135 Interacts with a Novel Centrosomal Protein (CPAP) Which Is Associated with the γ-Tubulin Complex
Author(s) -
LiangYi Hung,
Tang K. Tang
Publication year - 2000
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.20.20.7813-7825.2000
Subject(s) - biology , centrosome , tubulin , microtubule , microbiology and biotechnology , microtubule nucleation , immunoprecipitation , cell cycle , genetics , gene
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 (at -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 γ-tubulin are localized within the centrosome throughout the cell cycle. CPAP cosediments with γ-tubulin in sucrose gradients and coimmunoprecipitates with γ-tubulin, indicating that CPAP is a part of the γ-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.