SOX15 (also known as SOX20) is a nuclear, 25 kDa transcriptional repressor that belongs to group G of the SOX gene family. Human SOX15 is 233 amino acids (aa) in length and contains a 63 aa DNA-binding HMG-box (amino acids 48 - 110). Although the C-terminus (aa 126 - 233) does not bind DNA, it is required for SOX15 repressive activity. It may accomplish this by interacting with β-catenin. SOX15 is expressed in myoblasts and regulates skeletal muscle regeneration and differentiation. Human SOX15 shares 75% aa sequence identity with mouse SOX15.