Mouse cells contain two distinct ras gene mRNA species that can be translated into a p21 onc protein.

Abstract

The Kirsten (Ki) and Harvey (Ha) strains of murine sarcoma virus encode a 21,000-dalton protein (p21 ras) which is the product of the transforming gene of these viruses. Normal cells express low levels of p21 ras encoded by cellular genes (Ki-ras and Ha-ras) homologous to the Ki and Ha murine sarcoma virus transformation genes. A bone marrow-derived mouse cell line, 416B, has been shown to express unusually high levels of p21 ras. In this manuscript, we investigated the molecular biology of p21 ras gene expression in 416B and other normal mouse cells. We identified four distinct polyadenylated and polysomeassociated RNAs, two related to Ki-ras and two to Ha-ras. The levels in 416B cells of the two Ki-ras RNAs, sized 5.2 and 2.0 kilobases, were both elevated approximately 25-fold over levels found in normal mouse cells; there was no corresponding change in 416B cells in the levels of the two Ha-ras RNAs. We partially purified the two Ki-ras mRNAs and separated them by velocity sedimentation in sucrose density gradients. Both the 5.2-and 2.0-kilobase mRNAs could be translated in vitro into p21 ras. These results show that a cellular onc protein can be translated from two distinct cellular mRNA species.

Regulated transcription of c-Ki-ras and c-myc during compensatory growth of rat liver.

“…We compared the amount of c-/rasK and c-i-risH transcripts in polysomal poly(A)' RNA obtained from livers of normal and sham-operated rats and from regenerating livers at 12,18,24,36,48. and 96 h after partial hepatectomy by using the dot-blot procedure.…”

Developmentally-regulated expression of murine K-ras isoforms

“…Our studies of the same cells ( SW480, Calu-1, SK-N-SH, T24, peripheral blood lymphocytes) are broadly in agreement (DJW et al, unpublished data). Subsequent reports have used a restricted range of probes which would not distinguish the K-ras isoforms: HiHi 3 (Campisi et al, 1984;Ellis et al, 1981;Lockett and Sleigh, 1987;Sejersen et al, 1985), HiHi 380 (Ellis et al, 1981(Ellis et al, , 1982Goyette et al, 1984;Yaswen et al, 1985) and pY413 (George et al, 1985;Leon et al, 1987). Where PCR has been used, primers were chosen within exons 1 and 3 (Pal et al, 1993).…”

“…Where PCR has been used, primers were chosen within exons 1 and 3 (Pal et al, 1993). Two transcripts of the K-ras gene are translated into functional p21 K-ras (Ellis et al, 1982) but di er in the 3' untranslated region and poly(A) tail George et al, 1985;McGrath et al, 1983). The failure to note size heterogeneity even though both contain exon 4A and 4B sequences George et al, 1985) is probably due to inadequate resolution and low expression of the KrasA isoform.…”

Saccharomyces cerevisiae synthesizes proteins related to the p21 gene product of ras genes found in mammals.

“…5). In the cell extract made from the KC cells we in normal cells, and in some cases specific enhancement of expression has been detected in specialized cells or at precise stages of embryonic development (4,9 (1,6,23). In many cases, independent data have indicated that these homologs are expressed as mRNAs and proteins in many normal cells (8,10,26,27 with 0.007 ml of monoclonal antibody for 2 h at 4°C, followed by incubation with 0.060 ml of protein A-Sepharose coated with rabbit anti-rat immunoglobulin G for 1 h at 4°C.…”