Presence of a Kirsten murine sarcoma virus ras oncogene in cells transformed by 3-methylcholanthrene.

205

We examined the transcription of six cellular oncogenes during the process of compensatory growth in rat liver after partial hepatectomy. We have previously reported that transcripts of c-rasH are elevated during regenerative growth of the liver. We now report that transcripts of c-rasK and c-myc genes are significantly elevated after partial hepatectomy, whereas transcripts of c-abl and c-src are essentially unchanged and transcripts of c-mos are undetectable in either normal or regenerating rat liver. In liver regeneration after partial hepatectomy or chemical injury, changes in c-myc transcripts occur before DNA synthesis. The elevation of c-myc and c-ras transcripts is sequential in that highest levels of c-myc transcripts were detected 12 to 18 h after partial hepatectomy, whereas the levels of c-rasH and c-rasK were maximal by 36 to 48 h. Transcripts of all three activated oncogenes returned to their basal levels by 96 h.

Section: Resultsmentioning

confidence: 99%

“…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.…”

Section: Resultsmentioning

confidence: 99%

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

Goyette¹,

Petropoulos²,

Shank³

et al. 1984

205

“…Normal (cellular) ras genes acquire transforming properties by single point mutations within their coding sequences (4,32,33,41,(45)(46)(47)54), and these mutated ras genes have been detected in a significant fraction of human cancers as well as in experimentally induced animal tumors (45,48,54). It has been speculated that p21 ras proteins are essential components of normal cells that are involved in cell division and differentiation (30,31). Yet, little is known regarding the mechanisms by which p21 proteins induce malignant transformation, and even less is known regarding their role in normal cells.…”

mentioning

confidence: 99%

Insulin induction of Xenopus laevis oocyte maturation is inhibited by monoclonal antibody against p21 ras proteins.

Deshpande¹,

Kung²

1987

174

Microinjection of transforming p21 ras protein induces maturation of Xenopus laevis oocytes, and the induction is blocked by coinjection of monoclonal antibody (Y13-259) against p21 ras proteins. Similar to other inducing agents, the effect of p21 ras protein is mediated via the appearance of maturation or meiosispromoting factor activity. In addition, the neutralizing antibody markedly reduces oocyte maturation after insulin induction, whereas it fails to inhibit progesterone induction. Our results suggest that insulin induces maturation of oocytes via a different pathway than that of steroidal agents. The induction by insulin is ras dependent, and the action of ras may be directed at the steps before meiosis-promoting factor autocatalytic activation. These results suggest a role of p21 ras protein in the events associated with amphibian oocyte maturation.The ras family forms a group of closely related transforming genes that are highly conserved in eucaryotes (5,11,18,28,34,48). Normal (cellular) ras genes acquire transforming properties by single point mutations within their coding sequences (4,32,33,41,(45)(46)(47)54), and these mutated ras genes have been detected in a significant fraction of human cancers as well as in experimentally induced animal tumors (45,48,54). It has been speculated that p21 ras proteins are essential components of normal cells that are involved in cell division and differentiation (30,31). Yet, little is known regarding the mechanisms by which p21 proteins induce malignant transformation, and even less is known regarding their role in normal cells.It has been demonstrated that p21 proteins can induce transformation of NIH 3T3 cells when introduced by microinjection (13,44) and that the transforming activity of the ras proteins can be blocked by coinjection with monoclonal antibody Y13-259 (19). Recently, Birchmeier et al. (3) have shown that ras proteins can induce meiosis in Xenopus laevis oocytes. Fully grown oocytes can be easily injected and analyzed biochemically. Oocytes surgically removed from adult Xenopus ovaries are arrested in the prophase of meiosis and can be triggered to undergo meiosis by treatment with progesterone, insulin, and a variety of other agents. In the present study, we determined the effect of injected neutralizing antibody (Y13-259) on the maturation of oocytes.Gravid X. laevis females were obtained from Nasco Co. (Fort Atkinson, Wis.) and maintained under laboratory conditions (9). Ovarian fragments were surgically removed from frogs that were anesthetized by hypothermia. Fully grown stage VI oocytes were manually dissected, and follicle cells were removed after collagenase treatment of ovarian fragments at 21°C following the procedure of Eppig and Dumont (12) in modified Barth medium (MBSH) buffered with 5 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES), pH 7.6 (22). The selected stage VI oocytes were thoroughly washed in MBSH and equilibrated for at least 2 h before use. Oocytes were cultured in 30-mm Falcon * Corresponding author. ster...

“…The ability of the ras proteins to bind GTP (34,35) coupled with their inherent GTPase activity (9,22,39) has led to the hypothesis that these proteins work to regulate cell division and differentiation in normal cells (25,26). Transforming ras proteins display lowered GTPase activities and are presumed to inappropriately affect signalling processes within the cell, but their mechanism of action has not yet been elucidated.…”

Section: Discussionmentioning

confidence: 99%

“…The p21 proteins display guanine nucleotide binding (34, 35) and weak GTPase activity (9,22,39), and it has been proposed that they function as intracellular signal transducers. The working hypothesis contends that normal ras proteins play an important regulatory role in normal cell division and differentiation (25,26) and that the transforming actions of oncogenic mutants are due to altered biological function that in some way affects signalling action(s). One altered function that has been associated with transforming p21 proteins is decreased GTPase activity that results in an increased halflife of the p21-GTP complex (9,21,22,40 (8,15,(27)(28)(29)(30)33) by a novel mechanism that is independent of the classic guanine nucleotide-binding protein, termed G6 or Ni (12,24,30,33).…”

mentioning

confidence: 99%

Transforming ras proteins accelerate hormone-induced maturation and stimulate cyclic AMP phosphodiesterase in Xenopus oocytes.

Sadler¹,

Maller²,

Gibbs³

1990

Transforming Harvey (Ha) ras oncogene products accelerated the time course of Xenopus oocyte maturation induced by insulin, insulinlike growth factor 1, or progesterone. The transforming constructs, Ha p21and Ha p21, displayed equal potency and efficacy in their abilities to accelerate the growth peptide-induced response. Normal Ha p21 was only 60% as powerful and one-fifth as potent as the mutants containing valine in the 12 position. In contrast, two nontransforming constructs, Ha p21 and Ha(term-174) p21, had no effect on the time course of hormone-induced maturation. Effects of the transforming ras proteins on hormone-induced maturation correlated with their abilities to stimulate in vivo phosphodiesterase activity measured after microinjection of 200 ,IM cyclic [3H] AMP. When p21 injection followed 90 min of insulin treatment, there was no increase in phosphodiesterase activity over that measured after hormone treatment or p21 injection alone, but additive effects of p21 and insulin on enzyme activity were observed during the first 90 min of insulin treatment. Even though normal Ha p21 and transforming Ha p21 stimulated oocyte phosphodiesterase to equal levels when coinjected with substrate at the initiation of the in vivo assay, the transforming protein elicited a more sustained stimulation of enzyme activity. These results suggest that stimulation of a cyclic AMP phosphodiesterase activity associated with insulin-induced maturation is involved in the growth-promoting actions of ras oncogene products in Xenopus oocytes.The ras proteins make up a family of closely related gene products of approximately 21,000 molecular weight (also termed p21 proteins) that are highly conserved along evolutionary lines in both mammalian and lower eucaryotic cells (10). These proteins are membrane bound and display properties similar to elongation factor EF-Tu, ox-transducin, and the known guanine nucleotide-binding regulatory proteins of the adenylyl cyclase system (11, 14). The p21 proteins display guanine nucleotide binding (34, 35) and weak GTPase activity (9,22,39), and it has been proposed that they function as intracellular signal transducers. The working hypothesis contends that normal ras proteins play an important regulatory role in normal cell division and differentiation (25,26) and that the transforming actions of oncogenic mutants are due to altered biological function that in some way affects signalling action(s). One altered function that has been associated with transforming p21 proteins is decreased GTPase activity that results in an increased halflife of the p21-GTP complex (9,21,22,40 (8,15,(27)(28)(29)(30)33) by a novel mechanism that is independent of the classic guanine nucleotide-binding protein, termed G6 or Ni (12,24,30,33).Recently, induction of oocyte maturation by insulin and insulinlike growth factor 1 (IGF-1) was shown to correlate with both inhibition of adenylyl cyclase activity in membrane preparations and stimulation of phosphodiesterase measured in vivo after microinjection of 200 ,uM cycl...