Kinase Suppressor Of Ras 1 (KSR1)

In flies, activated RAS1 results in transformation of cone cells into R7 photoreceptor cells. The extra R7 cells cause the external surface of the eye to appear roughened, and the stronger the activating mutation the more roughness is observed. Using this system, the authors screened ethylmethanesulfonate-treated and x-ray-irradiated flies for mutations that would reduce or increase the roughness. One of the genes involved in modulating this phenotype was mapped, cloned, and shown to complement the mutation. Homologs of KSR were then identified in other species including C. elegans, mouse, and human. The mouse cDNA was isolated from a teratocarcinoma library and was predicted to encode an 873-amino acid protein that contains a kinase domain with similarity to a region of the RAF kinases.