Forkhead (FH) domain found in the Forkhead box protein K (FOXK) subfamily
The FOXK subfamily includes two winged helix transcription factors, FOXK1 and FOXK2. FOXK1, also called myocyte nuclear factor (MNF), acts as a transcriptional regulator that binds to the upstream enhancer region (CCAC box) of myoglobin genes. It positively regulates Wnt/beta-catenin signaling by translocating dishevelled (DVL) proteins into the nucleus. It also reduces virus replication, probably by binding the interferon stimulated response element (ISRE) to promote antiviral gene expression. In addition, FOXK1 plays important roles in multiple human cancers. FOXK2, also called cellular transcription factor ILF-1 or interleukin enhancer-binding factor 1, is a transcriptional regulator that recognizes the core sequence 5'-TAAACA-3'. It binds to NFAT-like motifs (purine-rich) in the IL2 promoter. It also binds to the HIV-1 long terminal repeat. FOXK2 may be involved in both, positive and negative regulation of important viral and cellular promoter elements. In addition, FOXK2 plays a critical role in suppressing tumorigenesis. The FH domain is a winged helix DNA-binding domain. FOX transcription factors recognize the core sequence 5'-(A/C)AA(C/T)A-3'.