Cell cycle control of p53 in normal (3T3) and chemically transformed (Meth A) mouse cells. II. Requirement for cell cycle progression.

TL;DRAbstract

To further characterize the role of p53 in growing normal Balb/c 3T3 fibroblasts, as well as of p53 in cells of the methylcholanthrene induced fibrosarcoma cell line Meth A, we analysed the effect of inhibition of p53 synthesis by microinjection of p53-specific monoclonal antibody PAb 122 into the nuclei of these cells after release from growth arrest induced by isoleucine starvation (see preceding paper [Steinmeyer et al., this issue] ). We show that microinjection of PAb 122, but not of control immunoglobulins, into the nuclei of both types of cells effectively blocked their re-entry into the S-phase of the cell cycle. Since isoleucine depletion of these cells was shown to lead to a growth arrest at the restriction point (R-point) in the G1-phase of the cell cycle, our results (i) define more precisely the role of p53 in growing cells as a protein controlling transition of the cells through this restriction point, and (ii) demonstrate that mutated p53 in Meth A cells still is functio

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