Cell Division Cycle

CDC42 (Cell division cycle 42 isoform 1) is a small GTPase of the Rho-subfamily that regulates signaling pathways which control various cellular functions including cell morphology, migration, endocytosis and cell cycle progression. CDC42 is a plasma membrane-associated small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state. In the active state, CDC42 binds to a variety of effector proteins to regulate cellular responses. CDC42 is involved in epithelial cell polarization processes. CDC42 causes the formation of thin, actin-rich surface projections called filopodia. Also, CDC42 regulates actin polymerization through its direct binding to N-WASP (Neural Wiskott-Aldrich syndrome protein), which subsequently activates Arp2/3 complex.
Loss of CDC42 function raises endocytotic uptake of apical proteins, as well as apical polarity factors such as Crumbs. The product of oncogene Dbl was described to specifically catalyze the dissociation of GDP from CDC42 protein.

CDC37, His protein is extremely parallel to Cdc 37, a cell division cycle control protein of Sacchromyces cerevisiae. CDC37 is a molecular chaperone with a detailed role in cell signal transduction. CDC37 forms a complex with Hsp90 and several protein kinases including CDK4, CDK6, SRC, RAF-1, MOK, and eIF2 alpha kinases CDC37 has a vital part in directing Hsp90 to its target kinases.

CDC37 is an essential protein in Saccharomyces cerevisiae and is a molecular chaperone with precise function in cell signal transduction. CDC37 forms a complex/associates with Hsp90 molecular chaperone as one of several auxiliary proteins that are collectively referred to as Hsp90 co-chaperones. CDC37 also forms complex with a number of protein kinases such as CDK4, CDK6, SRC, RAF-1, MOK, as well as eIF2 alpha kinases. CDC34 is involved in directing Hsp90 to its target kinases. CDC37 up-regulation is a common early event in some localized human cancers. CDC37 is necessary for maintaining prostate tumor cell growth and represents a novel target in the exploration for multitargeted therapies. CDC37 plays a role in regulating Hsp90 ATPase activity. CDC37 binds to Akt and HSP90 in the signal transduction pathway in human tumor cells. Tnf-induced recruitment and activation of the IKK complex require Cdc37 and Hsp90. CDC37 and heat shock protein 90 bind specifically to the kinase domain of LKB1.

CDC34 is important in the control of cell cycle and DNA replication. Cdc34 in association with different E3 complexes, including SCF, has been shown to target many different substrates for ubiquitination and degradation during cell division, signal transduction, and development. Cdc34 substrates that have been characterized include I?B, B-Myb, Wee1, MyoD, ICERII?, ATF5, p27Xic1, and p27Kip1. Additionally, substrates such as ?-catenin, p21Cip1, E2F, cyclin E, and cyclin D are putative substrates of Cdc34 by virtue of their SCF requirement for proteolysis. Cdc34 has been demonstrated to self-associate through a domain in the C-terminus, and is phosphorylated and ubiquitinylated in vivo. This protein is useful for in vitro ubiquitinylation reactions.

CDC34 takes part in the control of cell cycle and DNA replication. Cdc34 in association with different E3 complexes, including SCF, targets many different substrates for ubiquitination and degradation during cell division, signal transduction, and development. Cdc34 substrates that have been characterized include B-Myb, Wee1, MyoD, ATF5, p27Xic1, and p27Kip1. Additionally, substrates such as p21Cip1, E2F, cyclin E, and cyclin D are putative substrates of Cdc34 by virtue of their SCF requirement for proteolysis. Cdc34 is self-associate through a domain in the C-terminus, and is phosphorylated and ubiquitinylated in vivo. CDC34is useful for in vitro ubiquitinylation reactions.

CDC26 is a member of the CDC26 family which arranges progression via mitosis by enhancing cell-cycle regulators with ubiquitin chains. CDC26 is a component of the anaphase promoting complex/cyclosome (APC/C), which is a cell cycle-regulated E3 ubiquitin ligase which directs progression through mitosis and the G1 phase of the cell cycle. The APC/C complex operates by mediating ubiquitination and subsequent degradation of target proteins.

M-phase inducer phosphatase 1 (CDC25A) belongs to the CDC25 family of phosphatases. CDC25A is essential for progression from G1 to the S phase of the cell cycle. CDC25A activates the cyclin-dependent kinase CDC2 by eliminating 2 phosphate groups. CDC25A is specifically degraded in reaction to DNA damage, which inhibits cells with chromosomal abnormalities from progressing in the course of cell division. CDC25A is an oncogene, though its exact function in oncogenesis has not been determined.

CDC123 is a member of the CDC123 family. CDC123is required for S phase entry of the cell cycle. It is also broadly expressed in spleen,thymus, prostate, testis, ovary, small intestine, colon and leukocytes with the uppermost expression in testis.