Ubiquitin-ribosomal protein S27a gene overexpressed in human colorectal carcinoma is an early growth response gene.

One of the extension proteins on the carboxy terminus of ubiquitin was reported as the ribosomal protein S27a. We have cloned a gene which encodes this ubiquitin hybrid protein from a complementary DNA library of a human colon carcinoma cell line. Northern blot analysis of surgical specimens from colon cancer patients showed that these messenger RNA levels were higher in tumor tissue than in adjacent normal mucosa. Furthermore, to investigate the role of this novel ubiquitin hybrid gene in cellular growth control, the responsiveness of this gene to serum growth factors was examined. Within 30 min after serum or 12-O-tetradecanoylphorbol-13-acetate stimulation, its messenger RNA expression in rat fibroblast cells (Rat 1) was increased. Nuclear runoff transcription studies showed that the kinetics of induction of this gene is almost identical to that of protooncogene c-jun or c-fos, the known early growth response genes. Thus, this ubiquitin hybrid gene appears to be a novel early growth response gene overexpressed in human colon cancer and warrants further studies in the pathogenesis of colorectal carcinoma.