Major CDK9 elongation factor-associated protein (MCEF) is also known as AFF4 AF4/FMR2 family member 4. This family of proteins includes the AF4 proto-oncogene and FMR2 (fragile X E mental retardation syndrome) nuclear proteins. MCEF is a component of the cyclin-dependent kinase pair (CDK9/cyclin T1) complex. A chromosomal aberration involving AFF4 is found in acute lymphoblastic leukemia (ALL).
