Cleavage of the transactivation-inhibitory domain of p63 by caspases enhances apoptosis

doi:10.1073/pnas.0700761104

Cleavage of the transactivation-inhibitory domain of p63 by caspases enhances apoptosis

*Medical Research Council, Toxicology Unit, Leicester University, Leicester LE1 9HN, United Kingdom;
^†Department of Molecular Virology, Immunology, and Medical Genetics, Comprehensive Cancer Center, Ohio State University, Columbus, OH 43210; and
^‡Biochemistry Laboratory, IDI-IRCCS, University of Rome “Tor Vergata,” 00133 Rome, Italy

Edited by Peter K. Vogt, The Scripps Research Institute, La Jolla, CA, and approved May 8, 2007 (received for review January 29, 2007)

Abstract

p63 is a p53-related transcription factor. Utilization of two different promoters and alternative splicing at the C terminus lead to generation of six isoforms. The α isoforms of TAp63 and ΔNp63 contain a transactivation-inhibitory (TI) domain at the C termini, which can bind to the transactivation (TA) domain and inhibit its transcriptional activity. Consequently, TAp63α can directly inhibit its activity through an intramolecular interaction; similarly, ΔNp63α can inhibit the activity of the active TAp63 isoforms through an intermolecular interaction. In this work, we demonstrate that after induction of apoptosis, the TI domain of the p63α isoforms is cleaved by activated caspases. Cleavage of ΔNp63α relieves its inhibitory effect on the transcriptionally active p63 proteins, and the cleavage of TAp63α results in production of a TAp63 protein with enhanced transcriptional activity. In agreement with these data, generation of the N-terminal TAp63 fragment has a role in apoptosis because stable cell lines expressing wild-type TAp63 are more sensitive to apoptosis compared with cells expressing the noncleavable mutant. We also used a model system in which TAp63 expression was induced by trichostatin-A treatment in HCT116 cells. Trichostatin-A sensitized these cells to apoptosis, and this sensitization was associated with cleavage of up-regulated p63.

Footnotes

^§To whom correspondence may be addressed. E-mail: carlo.croce{at}osumc.edu
^¶To whom correspondence may be addressed at:
Medical Research Council, Toxicology Unit, Hodgkin Building, Leicester University, Lancaster Road, P.O. Box 138, Leicester, LE1 9HN, United Kingdom.
E-mail: gm89{at}leicester.ac.uk
Author contributions: B.S.S. and A.E.S. contributed equally to this work; B.S.S., A.E.S., G.M.C., R.A.K., C.M.C., and G.M. designed research; B.S.S., A.E.S., A.L.Y., R.I.A., E.C., and R.A.K. performed research; B.S.S. and A.E.S. contributed new reagents/analytic tools; B.S.S., A.E.S., G.M.C., R.A.K., C.M.C., and G.M. analyzed data; and B.S.S., A.E.S., R.A.K., C.M.C., and G.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0700761104/DC1.
Abbreviations:

HDAC,

histone deacetylase;

PARP,

poly(ADP-ribose) polymerase;

TA domain,

transactivation domain;

TI domain,

transactivation-inhibitory domain;

TSA,

trichostatin-A;

z-VAD-fmk,

Z-Val-Ala-Asp-fluoromethyl ketone.