Reversion of a human tumour cell line containing oncogenic p21ras is associated with a defect in the post-translational processing of the ras protein
Tilbrook, P.A.; Paterson, H.F.; Marshall, C.J.
Oncogene 10(4): 805-809
1995
ISSN/ISBN: 0950-9232 PMID: 7862461 Document Number: 448353
Correct post-translational modifications of the ras proteins are essential for their membrane localization and functioning. The flat revertant cell lines 1aCB and 8b, derived from the human bladder carcinoma cell line EJ, contain the transforming gene V12Ha-ras and are resistant to retransformation by ras protein or DNA, but still do require the presence of ras for proliferation. Both revertant cell lines demonstrated reduced levels of membrane associated p21-ras when compared to their parental EJ cell lines. This reduced level in 1aCB was reflected by an increase in nuclear associated p21-ras, as seen by immunofluorescence of endogenous and introduced ras. In addition, 1aCB had a reduced ratio of ras in the detergent to aqueous phases after triton X114 partitioning, suggesting a defect in Step I processing of the p21-ras in the cell line. This was not however due to defects in the Step I enzymes farnesyltransferase or carboxymethyltransferase whose activities were not reduced.