Sex, Sox, and splicing

Mammalian sex-determining factors with homology to DNA binding proteins are required for splicing, according to a study by Paolo Sassone-Corsi and coworkers at the Université Louis Pasteur (Strasbourg, France). Examination of high mobility group (HMG) domain containing SRY and Sox proteins demonstrated a surprising but clear association with splicing complexes.

SRY, the testis-determining factor found on the Y-chromosome in mice and humans, is one of several Sox family members involved in sexual development. It is known to bind DNA, in support of the proposal that HMG domain proteins act as architectural facilitators for building transcription complexes.

Sassone-Corsi's group thus expected to find Sox proteins colocalized in the nucleus with transcription factors. Instead, SRY and SOX6 proteins associated with splicing factors in nuclear speckle domains. Depletion of SOX6 in HeLa cell extracts blocked splicing...