Enables cyclin-dependent protein serine/threonine kinase regulator activity; kinase activity; and protein kinase binding activity. Acts upstream of or within several processes, including DNA metabolic process; homologous chromosome pairing at meiosis; and negative regulation of transcription by RNA polymerase II. Located in nucleus. Part of cyclin E1-CDK2 complex. Is expressed in several structures, including brain; early conceptus; embryo ectoderm; eye; and spinal cord. Human ortholog(s) of this gene implicated in breast adenocarcinoma. Orthologous to human CCNE1 (cyclin E1). [provided by Alliance of Genome Resources, Apr 2022]