GTP-binding protein Di-Ras3 (DIRAS3) also known as aplysia ras homology member I (ARHI) is a protein that in humans is encoded by the DIRAS3 gene.
This gene is a member of the Ras superfamily and is expressed in normal ovarian and breast epithelial cells but not in ovarian and breast cancers. It is a maternally imprinted gene, with monoallelic expression of the paternal allele, which is associated with growth suppression. Thus, this gene appears to be a putative tumor suppressor gene whose function is abrogated in ovarian and breast cancers.
DIRAS3 is linked to breast cancer as well as ovarian cancer. The DIRAS3 gene includes one promoter, two exons and one intron with a 687 bp protein-coding region that encodes a 26-kDa protein. The DIRAS3 protein is a GTPase belonging to the Ras superfamily and shares 50–60% homology with Ras and Rap, two other small GTP binding proteins. Reduced expression of DIRAS3 has been reported in 70% of invasive breast cancers.
