Chromatin structure of the promoter region of the human c-K-ras gene.

The chromatin structure of the human c-K-ras gene has been investigated in various cultured normal and tumor human cells and in a rat cell line transformed with the human oncogene. The promoter region is hypersensitive to DNAse I, micrococcal nuclease, endogenous nucleases and to S1 nuclease in supercoiled plasmids. This hypersensitive region is present in the different cell types analyzed and both normal and mutant alleles exhibit similar general sensitivity to DNAse I digestion in the same tumor cells. However, the 5' more distal DNAse I hypersensitive site, which is coincident with a region of the gene containing sequence homologies with known enhancers, exhibits variable sensitivity which appears to be higher in the tumor than in the normal and in the human than in the rat cells which we have analyzed. These data suggest the presence of specific factors interacting with the promoter sequences and delimits the transcription unit of the c-K-ras locus.