Role of the p53 protein in cell proliferation as studied by microinjection of monoclonal antibodies.

Abstract

Two monoclonal antibodies against the p53 protein, PAb 122 and 200-47, were microinjected into mammalian cells as a probe to determine the role of the p53 protein in cell proliferation. PAb 122 recognizes the p53 proteins of mouse and human cells but not of hamster cells, whereas 200-47 recognizes the p53 proteins of mouse and hamster cells but not of human cells. The ability of these antibodies to inhibit serumstimulated DNA synthesis of cells in culture correlates with their ability to recognize the species-specific antigenic determinants. More important, however, is the observation that microinjected PAb 122 inhibits the transition of Swiss 3T3 cells from Go to S phase, but has no effect on the progression of these cells from mitosis to the S phase.The p53 protein is a transformation-related protein that is often present in higher amounts in transformed cells than in their normal, untransformed counterparts (7,10,18,25). It has been detected in cells transformed by DNA viruses (16,17), by RNA viruses (25,27), by chemicals and X-rays (10), and in several human tumor cell lines (7). Although present in uninfected embryonal carcinoma cells (17), it is not detectable in 3T3 cells (10) and in several untransformed cell strains (7). The synthesis of the p53 protein is markedly increased in mixed populations of lymphocytes stimulated by concanavalin A (21, 22). Its relationship to actively dividing cells has suggested to a number of investigators that the p53 protein may play a role in the regulation of cell proliferation (6, 11,17,22).In a previous paper (19) we have shown that microinjection of a monoclonal antibody against the p53 protein (ap53) inhibited the entry into S phase of quiescent Swiss 3T3 cells stimulated by serum. The inhibitory effect was observed only when ap53 was microinjected about the time of serum stimulation. In this paper, we extended our studies on the effect of microinjected ap53 on cells from different species, on the accumulation of cellular DNA, and on the progression of Swiss 3T3 cells from mitosis through G, to S phase. MATERIALS AND METHODSCell lines and culture conditions. The Syrian hamster G1-specific, temperature-sensitive mutant cell line ts13 was maintained under culture conditions as previously described in detail (2, 12 cells per 60-mm petri dish in growth medium containing 1% calf serum, followed by 5 to 7 days of incubation at 37°C for Swiss 3T3 and WI-38 or at 34°C for ts13. At this time, the cells were quiescent (see below) and could be used for serum stimulation and microinjection.Microinjection procedure. The glass-capillary microinjection method of Graessmann and Graessmann (14) and the modifications for antibody microinjection have been described previously (12, 19, 20). Briefly, a small circle was etched on a 22-mm2 glass cover slip before the cells were plated for quiescence. All, or nearly all, of the cells within the circle were microinjected, and the cells outside of the circle (treated in exactly the same way except for microinjection) served as background contr...

Correlation of DNA content, p53, T antigen, and V antigen in simian virus 40‐infected human diploid cells

“…Since p53 has been detected at low levels in normal murine and primate cells (1) but elevated in SV4O-infected and -transformed cells, the function of p53 in each of these systems has been the subject of numerous investigations. A putative function of p53 is the regulation of the cell cycle by controlling exit of cells from Go (33). Given the stable association of p53 with SV40-T antigen in the transformed state (321, the hypothesis has been made that the high levels of p53 which result from this association play a n important part in the induction of transformation.…”

The relationship of p53 immunostaining to survival in carcinoma of the lung

“…The subsequent protein products are believed to exert negative control on the cell cycle, regulating passage into the S phase of DNA replication (Mercer et al, 1984). Thus an abnormally low level of wild-type p53 results in a deficiency of the regulatory proteins, allowing largely uncontrolled cell division.…”

Mutations in p53 do not account for heritable breast cancer: a study in five affected families

“…Normal p53 is found at low levels in virtually all mammalian cells (Rogel et al, 1985) and various studies have shown elevated levels of the mRNA and protein in a wide variety of tumours and tumour cell lines (Linzer & Levine, 1979;De Leo et al, 1979;Crawford et al, 1981;Benchimol et al, 1982;Rotter, 1983;Thomas et al, 1983) including breast cancer (Cattoretti et al, 1988;Thompson et al, 1990). The normal function of p53 is not known, but it is thought to be involved in the GO/GI to S transition in the cell cycle (Mercer et al, 1984;Ganon & Lane, 1987) where regulation of its activity may be through phosphorylation. Evidence suggests that p53 may behave as a negative regulator, that it is essential for normal growth and that its inactivation may be necessary for the development of malignancy (Lane & Benchimol, 1990).…”