Wilms' tumor 1-associating protein (WTAP) was previously identified as a protein associated with Wilms' tumor-1 (WT-1) protein that is essential for the development of the genitourinary system. WT1 was originally identified as a tumor suppressor for Wilms' tumor, but it is also overexpressed in a variety of cancer cells. The WTAP-WT1 axis in vascular cells suggest that WTAP is a vital and multifaceted regulator of vascular remodeling. WTAP has been suggested to function in alternative splicing, stabilization of mRNA, and cell growth. Knocking down endogenous WTAP increased Smooth muscle cells (SMCs) proliferation, because of increased DNA synthesis and G(1)/S phase transition, together with reduced apoptosis. These effects could be the result of WTAP suppressing the transcriptional activity of WT1 in SMCs. WTAP may thus also play a role in messenger RNA processing in mammalian cells, either dependent on or independent of its interaction with WT1.