Abstract: The present invention relates to complexes of the CDK2 protein with proteins identified as interacting with CDK2 by a modified yeast two hybrid assay system. The proteins identified to interact with CDK2 are cyclin H, cyclin I, ERH, and two gene products, hsReq*-1 and hsReq*-2, which are splice variants of the gene hsReq. Thus, the invention provides complexes of CDK2 and cyclin H, cyclin I, ERH, hsReq*-1, and hsReq*-2, and derivatives, fragments and analogs thereof. The invention also provides nucleic acids encoding the hsReq*-1 and hsReq*-2, and proteins and derivatives, fragments and analogs thereof. Methods of screening the complexes for efficacy in treating and/or preventing certain diseases and disorders, particularly cancer, atherosclerosis and neurodegenerative disease are also provided.