Abstract
We have examined the domain-specific interactions between p53 and poly(ADP-ribose)polymerase (PARP) (E.C. 2.4.2.30) in apoptotic HeLa cells. Apoptosis was induced by exposing cells to 50 µm N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) for increasing lengths of time and was confirmed by: (a) oligonucleosomal fragmentation of chromatin; (b) increase in p53 levels; and (c) degradation of PARP into the characteristic Mr 85,000 (COOH-terminal catalytic domain) and Mr 29,000 (DNA-binding domain) peptide fragments. We also immunodetected p53 in immunoprecipitates obtained with a PARP-specific antibody. However, intact PARP coimmunoprecipitated with a p53-specific antibody during the initial 30 min of MNNG treatment. After 60 min, only the COOH-terminal fragment coimmunoprecipitated with p53, indicating that PARP noncovalently binds p53 via its Mr 85,000 catalytic domain. Therefore, we next examined p53 as a covalent target for poly(ADP-ribosyl)ation. Although p53 was not endogenously poly(ADP-ribosyl)ated in situ, incubation of cell extracts with full-length PARP from calf thymus and [32P]βNAD+ resulted in its time-dependent poly(ADP-ribosyl)ation. In summary, our results are consistent with the conclusion that PARP and p53 are activated with nonoverlapping kinetics during apoptosis.
Footnotes
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↵1 This project was supported by Grant 9678-014 from the Texas Advanced Research Program and Grant GM45451 from the NIH.
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↵2 To whom requests for reprints should be addressed, at Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107-2699. Phone: (817) 735-2117; Fax: (817) 735-2118; E-mail: ralvarez@hsc.unt.edu.
- Received July 14, 1998.
- Accepted September 24, 1998.
- ©1998 American Association for Cancer Research.