SOS1 Gene

SOS1 (SOS Ras/Rac Guanine Nucleotide Exchange Factor 1) is a protein-coding gene located on chromosome 2p22.1

The SOS1 gene encodes a protein that is a guanine nucleotide exchange factor for RAS proteins, membrane proteins that bind guanine nucleotides and participate in signal transduction pathways. GTP binding activates and GTP hydrolysis inactivates RAS proteins (Chardin P et al 1993).

The SOS1 protein encoded by this gene may regulate RAS proteins by facilitating the exchange of GTP for GDP. Mutations in this gene are associated with:

• gingival fibromatosis 1
• and
• Noonan syndrome type 4 .

Furthermore, it promotes the exchange of Ras-bound GDP for GTP (Chardin P et al. 1993) and presumably regulates the phosphorylation of MAP kinase MAPK3 in response to EGF by promoting Ras activation (Modzelewska K et al. (2007). The SOS1 protein forms the catalytic component of a trimeric complex involved in the transduction of signals from Ras to Rac by promoting the activity of Rac-specific guanine nucleotide exchange factor (GEF)

1. Chardin P et al. (1993) Human Sos1: a guanine nucleotide exchange factor for Ras that binds to GRB2. Science 260:1338-1343.
2. Modzelewska K et al. (2007) An activating mutation in sos-1 identifies its Dbl domain as a critical inhibitor of the epidermal growth factor receptor pathway during Caenorhabditis elegans vulval development. Mol Cell Biol 27:3695-3707.
3. Gawron K et al (2017) Analysis of mutations in the SOS-1 gene in two Polish families with hereditary gingival fibromatosis. Oral Dis 23:983-989.
4. Liakou AI et al (2014) Triad of keratosis pilaris, ulerythema ophryogenes and 18p monosomy: Zouboulis syndrome. J Dermatol 41:371-376.