E4F1, also known as E4F, is a 784 amino acid protein that localizes to both the nucleus and the cytoplasm and contains nine C2H2-type zinc fingers. Expressed ubiquitously in adult and fetal tissues, E4F1 exists as a homodimer that binds DNA and is thought to act as a transcriptional repressor and may also play a role in cell survival and growth via cell cycle control. Additionally, E4F1 is thought to function as a ubiquitin ligase that mediates the ubiquitination (and subsequent degradation) of target proteins and may be involved in the p53 tumor suppressor pathway. E4F1, which may be post-translationally phosphorylated or sumoylated, is subject to proteolytic cleavage which results in the creation of a short peptide with specific DNA binding capabilities.