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p53 in human embryonal carcinoma: identification of a transferable, transcriptional repression domain in the N-terminal region of p53.

Abstract
Testicular germ cell tumors (TGCTs) arise despite possessing high levels of wild-type p53, suggesting p53 latency. We have previously shown that p53 repression in TGCT-derived human embryonal carcinoma (EC) is relieved upon treatment with all-trans retinoic acid (RA), resulting in enhanced p53 transactivation activity. To further investigate p53 repression in EC, a series of gal4-p53 truncation constructs were generated. Deletion of the core DNA-binding region, residues 117-274, had no effect on basal or RA-induced p53 activity. Progressively, larger truncations were made in the C- or N-terminal direction. Deletion of residues toward the C-terminus of p53 as far as residue 354 did not affect either the basal or RA-inducible activity of gal4-p53. When a small region in the N-terminus was deleted (residues 105-116), relief of the basal repression of p53 activity characteristic of EC was observed. Fusion of this region to the VP16 activation domain (VPAD) resulted in a 10-20-fold repression of VPAD activity in NT2/D1 human EC cells, indicating that this region acts as a heterologous repressor. Owing to its location in the N-terminal half of p53, we have named this region the p53 N-terminal Repression Domain (p53-NRD). The p53-NRD mediated repression in a variety of cell lines, with the most prominent repression observed in human EC cells. While RA alone had no effect on p53-NRD activity, cotreatment with RA and the histone deacetylase inhibitor trichostatin-A (TSA) completely relieved p53-NRD-mediated repression. In contrast, NRD-mediated repression was not sensitive to RA and TSA in a derived RA-resistant cell line with a retinoic acid receptor gamma (RARgamma) defect, but sensitivity could be restored with transfection of RARgamma. These data indicate that a unique repressor domain resides in p53 at residues 90-116 whose activity can be modulated in the presence of 'differentiation therapy' and 'transcription therapy' agents.
AuthorsJoshua C Curtin, Michael J Spinella
JournalOncogene (Oncogene) Vol. 24 Issue 9 Pg. 1481-90 (Feb 24 2005) ISSN: 0950-9232 [Print] England
PMID15674351 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Tumor Suppressor Protein p53
  • Tretinoin
Topics
  • Amino Acid Sequence
  • Animals
  • Breast Neoplasms
  • CHO Cells
  • COS Cells
  • Carcinoma, Embryonal (genetics)
  • Cell Division (drug effects)
  • Cell Line, Tumor
  • Chlorocebus aethiops
  • Cricetinae
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Molecular Sequence Data
  • Transcription, Genetic (genetics)
  • Transfection
  • Tretinoin (pharmacology)
  • Tumor Suppressor Protein p53 (chemistry, genetics)

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