FOXO3 belongs to the O subclass of the forkhead family of transcription factors which are characterized by a distinct fork headDNA-binding domain. There are three other FoxO family members in humans, FOXO1, FOXO4 and FOXO6. These transcription factors share the ability to be inhibited and translocated out of the nucleus on phosphorylation by proteins such as Akt/PKB in the PI3K signaling pathway (aside from FOXO6, which may be constitutively nuclear). Other post-translational modifications including acetylation and methylation are seen and can result in increased or altered FOXO3a activity.
It is thought that FOXO3a is also involved in protection from oxidative stress by upregulating antioxidants such as catalase and MnSOD. Ron DePinho's group generated Foxo3 knockout mice, and showed that female exhibit a dramatic age-dependent infertility, due to premature ovarian failure.
Deregulation of FOXO3a is involved in tumorigenesis, for example translocation of this gene with the MLL gene is associated with secondary acute leukemia. Downregulation of FOXO3a activity is often seen in cancer (e.g. by increase in Akt activity resulting from loss of PTEN). FOXO3 is known as a tumour suppressor.
Alternatively spliced transcript variants encoding the same protein have been observed.
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