Inhibitors of USP1 deubiquitinating enzyme complex

A composition comprising an isolated USP1 polypeptide comprising the sequence of SEQ ID NO:

• 3 or a sequence at least 95% identical thereto, and an isolated UAF1 polypeptide comprising the sequence of SEQ ID NO:
• 4 or a sequence at least 95% identical thereto.

A method of identifying an inhibitor of USP1 deubiquitinase, comprising:

• contacting USP1 with a test compound in the presence of monoubiquitinated PCNA, monoubiquitinated FANCD2, or ubiquitin-7-amido-4-methylcoumarin;
• and
• measuring the deubiquitination of said PCNA, FANCD2, or ubiquitin-7-amido-4-methylcoumarin, wherein a decrease in the deubiquitination of said PCNA, FANCD2, or ubiquitin-7-amido-4-methylcoumarin in the presence of the test compound relative to the absence of the test compound identifies said test compound as an inhibitor of USP1 deubiquitinase.

A method for identifying an inhibitor of USP1 deubiquitinase, comprising

• measuring the deubiquitinase activity of USP1 in the presence and absence of a test compound, wherein a decrease in deubiquitinase activity in the presence of the test compound identifies said compound as an inhibitor of USP1 deubiquitinase.

The method of claim 18, wherein said cell is a cancer cell.

A method for identifying an inhibitor of USP1 deubiquitinase, comprising:

• contacting a composition comprising USP1 and UAF1 with a test compound in the presence of ubiquitin-7-amido-4-methylcoumarin;
• and
• measuring the deubiquitination of said ubiquitin-7-amido-4-methylcoumarin, wherein a decrease in the deubiquitination of ubiquitin-7-amido-4-methylcoumarin in the presence of the test compound relative to the absence of the test compound identifies said test compound as an inhibitor of USP1 ubiquitinase.

A method of identifying a compound as a compound useful for the treatment of genotoxin exposure, comprising

• measuring USP1 deubiquitinase activity in the presence and absence of a test agent;
• and
• determining whether said USP1 deubiquitinase activity is decreased in the presence of said test agent, wherein if said activity is decreased in the presence of said test agent, scoring said test agent as a compound useful for the treatment of genotoxin exposure.

A method of identifying a compound as a compound useful for the treatment of cancer, comprising

• measuring USP1 deubiquitinase activity in the presence and absence of a test agent;
• and
• determining whether said USP1 deubiquitinase activity is decreased in the presence of said test agent, wherein if said activity is decreased in the presence of said test agent, scoring said test agent as a compound useful for the treatment of cancer.

A method of identifying a cytoprotective agent, comprising:

• contacting a cell with a candidate inhibitor of USP1 deubiquitinase;
• and
• exposing the cell to a genotoxic agent, and measuring cell survival, wherein if cell survival is increased, the candidate inhibitor is identified as a cytoprotective agent.

A method of diagnosing cancer or an increased susceptibility to cancer in an individual comprising:

• measuring the level of USP1 and UAF1 in a cell from said individual, wherein an increase in the level of USP1 and UAF1 in said cell relative to a control is indicative of said individual having cancer or an increased susceptibility to cancer.

A method of diagnosing cancer or an increased susceptibility to cancer in an individual comprising:

• measuring the binding of UAF1 to USP1 in a sample from said individual, wherein an increase in the binding of UAF1 to USP1 in said cell relative to a control is indicative of said individual having cancer or an increased susceptibility to cancer.