Transcription Factor Stat5 in Invasion and Metastatis of Human Breast Cancer
Annual summary rept. 15 Apr 2005-14 Apr 2006
GEORGETOWN UNIV WASHINGTON DC
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Class IA PI3Ks are regarded the most important in regulating cell proliferation and tumorigenesis. The p55gamma protein is a regulatory subunit of class IA PI3K. In vitro study has demonstrated that the NH2-terminal of p55gamma is sufficient to bind the cell cycle regulatory protein pRb. Direct association between Cacalmodulin and p85 subunit of PI3K has been demonstrated by coimmunoprecipitation and affinity chromotography. Cacalmodulin directly interact with SH2 domains of p85, resulting inactivation of p110. The NH2-terminal and COOH terminal of p55gamma SH2 domains are 89 and 81 identical with that of p85 ,respectively. Here we addressed the issue of whether p55gamma associates with calmodulin in vitro in human 293T cells. Using calmodulin-conjugated sepharose beads we analyzed the Flag-tagged p55gamma cDNA transfected cells. The cell cycle profile of HEK293 cells stable expressing Flag-tagged p55gamma were analyzed by flow cytometry. Our experiments demonstrated that overexpression of p55gamma in HEK293 cells promoted cell cycle progression. Our data also show a calcium-dependent calmodulin-p55gamma interaction in human 293T cells, and the overexpression of FLAG-tagged p55gamma stabilized the interaction between calmodulin and retinoblastoma protein. We propose that p55gamma protein regulate cell cycle progression through formation of a ternary complex with calmodulin and Rb.
- Genetic Engineering and Molecular Biology
- Medicine and Medical Research