| Modification Notes |
The homeobox DNA-binding domain is a 60 amino acid motif that is conserved among many species and functions to bind DNA via a helix-turn-helix structure, thereby playing a role in transcriptional regulation and the control of gene expression. ISX (intestine-specific homeobox), also known as Pix-1 or RAXLX, is a 245 amino acid protein that localizes to the nucleus and contains one homeobox DNA-binding domain. Present at high levels in intestinal epi-thelial cells, ISX functions as a transcription factor that regulates intestinal gene expression and may also participate in vitamin A metabolism via the regulation of BCMO1 expression. The gene encoding ISX maps to human chromosome 22, which houses over 500 genes and is the second smallest human chromosome. Mutations in several of the genes that map to chromosome 22 are involved in the development of Phelan-McDermid syndrome, neurofibromatosis type 2, autism and schizophrenia. |