SKOR gene family

Genes in the SKOR gene family provide instructions for making proteins called SKI transcriptional corepressors. These proteins are able to stop (repress) the first step in the production of proteins from genes, a process known as gene transcription. They repress transcription by blocking signaling pathways that turn on gene activity, in particular the transforming growth factor beta (TGF-β) pathway and the bone morphogenic protein (BMP) pathway.

Signaling through the TGF-β and BMP pathways turns on (activates) proteins called SMADs, which combine to form a protein complex. The activated SMAD protein complex moves to the nucleus and attaches (binds) to specific areas of DNA to activate gene transcription. The TGF-β and BMP pathways are able to regulate various cellular processes, including cell growth and division (proliferation), the process by which cells mature to carry out special functions (differentiation), and the self-destruction of cells (apoptosis).

SKI transcriptional corepressors control the activity of the TGF-β and BMP pathways by attaching (binding) to certain SMAD proteins, which interrupts signaling through the pathways. SKI transcriptional corepressor binding within the cell can keep the SMAD protein complex from entering the nucleus, so it is unable to control gene activity. Binding of the SKI transcriptional corepressor can also occur in the nucleus, where it allows the SMAD protein complex to attach to DNA, but blocks its ability to turn genes on.

The SKI transcriptional corepressors are important during development and throughout life. The SKI and SKIL proteins, two members of this family, are found in many cell types throughout the body and appear to play a role in the development of many tissues, including bones, muscles, and the brain. Mutations in the SKI gene lead to a disorder called Shprintzen-Goldberg syndrome, which affects many parts of the body and is characterized by distinctive facial features and skeletal and neurological abnormalities. Two other SKI transcriptional corepressors, SKOR1 and SKOR2, are found only in the nervous system, particularly in a region of the brain called the cerebellum. These proteins appear to be important for proper development of this part of the brain.