Enables MDM2/MDM4 family protein binding activity, enzyme inhibitor activity, and protein N-terminus binding activity. Involved in several processes, including negative regulation of lymphocyte proliferation, positive regulation of apoptotic process, and regulation of transcription, DNA-templated. Acts upstream of or within several processes, including negative regulation of cellular protein metabolic process, negative regulation of mammary gland epithelial cell proliferation, and positive regulation of apoptotic process involved in mammary gland involution. Located in cytoplasm and granular component. Part of protein-containing complex. Is expressed in several structures, including bone marrow, central nervous system, dorsal root ganglion, eye, and testis. Human ortholog(s) of this gene implicated in several diseases, including breast cancer (multiple), carcinoma (multiple), hematologic cancer (multiple), melanoma (multiple), and nervous system cancer (multiple). Orthologous to human CDKN2A (cyclin dependent kinase inhibitor 2A).