Microinjection of the oncogene form of the human H-ras (t-24) protein results in rapid proliferation of quiescent cells

Ras p21 in breast tissue: associations with pathology and cellular localisation

“…The age-related decline in p21 expression of normal TDLU epithelium also parallels a decline in proliferation rate (Going et al, 1988b). It is of course very well established that ras proteins mediate cell proliferation in a variety of other cell types (Feramisco et al, 1984;Mulcahy et al, 1985;Downward et al, 1990). Nevertheless, p21 expression is also a feature of non-proliferating cells, such as the myoepithelium described here (Joshi et al, 1986) and many other cell types (Spandidos & Dimitrov 1985;Chesa et al, 1987).…”

Myb binding sites within the N-ras promoter repress transcription

“…N-ras, Hras, and K-ras are three members of this ras family and encode similar yet non-identical proteins that have been implicated in the normal cellular processes of proliferation (Feramisco et al, 1984;Mulcahy et al, 1985) and di erentiation (Bar-Sagi and Feramisco, 1985;Noda et al, 1985;Guerrero et al, 1986), as well as the process of transformation (Der et al, 1982;Santos et al, 1982). These 21 kD proteins (p21), serve as signal transducing molecules by conformationally switching from an inactive state (GDP-bound) to an active state (GTP-bound) upon receiving a signal.…”

Expression of c-fos and AP-1 activity in senescent human fibroblasts is not sufficient for DNA synthesis.

“…The ras protein was purified from an F~cherichia coli expression vector system (Gross et al, 1985) to near homogeneity as in Feramisco et al (1984). Inert carrier IgG (Sigma Chemical Co., St. Louis, MO) was coinjected with all samples at a concentration of 2 mg/ml to allow the definitive identification of all microinjected cells.…”

“…Microinjection of oncogenic ras protein into quiescent fibroblasts has been shown to result in changes in cell morphology (Feramisco et al, 1984), induction of c-fos expression (Stacey et al, 1987), and initiation of DNA synthesis. In contrast, senescent human fibroblasts injected with oncogenic c-Ha-ms expression vectors (Lumpkin et al, 1986) fail to synthesize DNA.…”