Patent ID: 6881575

Claim:
A method for screening for compounds capable of specifically inhibiting or abrogating the G2 cell cycle arrest checkpoint comprising the following steps: (a) providing a test compound; (b) providing the polypeptide of SEQ ID NO: 1897, which polypeptide is capable of inhibiting or abrogating the G2 cell cycle arrest checkpoint and acts as a G2 checkpoint inhibiting positive control; (c) providing isolated G1 checkpoint impaired cells; (d) contacting a first sample of said G1 checkpoint impaired cells with a DNA damaging agent or treatment to activate the G2 phase cell cycle arrest checkpoint; (e) contacting a second sample of said G1 checkpoint impaired cells with an agent that specifically arrests the cell cycle at the M phase; (f) culturing a portion of said first and second samples of contacted cells in the presence or absence of the test compound; (g) culturing a portion of said first and second samples of contacted cells in the presence or absence of the polypeptide; (h) measuring DNA content of said portions of contacted cells cultured in the presence or absence of the test compound or polypeptide to determine the fraction of the cells in the G2 and M phases of the cell cycle; (i) identifying the test compound as capable of specifically inhibiting or abrogating the G2 cell cycle arrest checkpoint if: (1) the fraction of the portion of said first sample of contacted cells cultured in the presence of the test compound determined to be in the G2 phase of the cell cycle decreases relative to the fraction of the portion of said first sample of contacted cells cultured in the absence of the test compound determined to be in the G2 phase of the cell cycle; and (2) the fraction of the portion of said second sample of contacted cells cultured in the presence of the test compound determined to be in the M phase of the cell cycle does not differ significantly from the fraction of the portion of said second sample of contacted cells cultured in the absence of the test compound determined to be in the M phase of the cell cycle; wherein the identification is validated by the positive control if: (1) the fraction of the portion of said first sample of contacted cells cultured in the presence of the polypeptide determined to be in the G2 phase of the cell cycle decreases relative to the fraction of the portion of said first sample of contacted cells cultured in the absence of the polypeptide determined to be in the G2 phase of the cell cycle; and (2) the fraction of said contacted cells cultured in the presence of the polypeptide determined to be in the M phase of the cell cycle does not differ significantly from the fraction of said contacted cells cultured in the absence of the polypeptide determined to be in the M phase of the cell cycle.