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The in Vivo DNA Binding Properties of Wild-type and Mutant p53 Proteins in Mammary Cell Lines During the Course of Cell Cycle.

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Annual rept. 1 Jul 94-30 Jun 95,

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We are investigating what forms of p53 bind to potential p53 DNA binding sequences in vivo by carrying out a systematic study of the interactions of wild-type and mutant p53 with the p53 responsive regions of genes in their native chromatin structure. Although we have not begun to investigate the in vivo DNA binding ability of p53 in the breast cancer cell lines, we have set up a system to identify conditions under which p53 binding sites in vivo demonstrate DNasel sensitivity in the absence of wild-type p53, and resistance in the presence of p53, at the p53 responsive region of the mdm2 gene in a mouse embryo fibroblast cell line. We have identified the cytoplasmic, nuclear and whole cell levels of p53 in the breast cancer cell lines ZR75-1 wtp53 -, MDA-MB-468 273 Arg to His and MDA- MB-157 null for p53 by deletion. MDA-MB-468 has a high nuclear level of p53 protein while ZR75-1 cells contain a very low level of wild-type p53 and there is no detectable p53 in MDA-MB-157. Interestingly, we have stabilized both the nuclear and cytoplasmic forms of p53 in ZR75-1 with an inhibitor of the ubiquitin proteolytic pathway.

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  • Biochemistry
  • Anatomy and Physiology
  • Medicine and Medical Research

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