TReP-132 controls cell proliferation by regulating the expression of the cyclin-dependent kinase inhibitors p21WAF1/Cip1 and p27Kip1

Mol Cell Biol. 2005 Jun;25(11):4335-48. doi: 10.1128/MCB.25.11.4335-4348.2005.

Abstract

The transcriptional regulating protein of 132 kDa (TReP-132) has been identified in steroidogenic tissues, where it acts as a coactivator of steroidogenic factor 1 (SF-1). We show here that TReP-132 plays a role in the control of cell proliferation. In human HeLa cells, TReP-132 knockdown by using small interfering RNA resulted in increased G(1)-->S cell cycle progression. The growth-inhibitory effects of TReP-132 was further shown to be mediated by induction of G(1) cyclin-dependent kinase inhibitors p21(WAF1) (p21) and p27(KIP1) (p27) expression levels. As a consequence, G(1) cyclin/cyclin-dependent kinase activities and pRB phosphorylation were markedly reduced, and cell cycle progression was blocked in the G(1) phase. The stimulatory effect of TReP-132 on p21 and p27 gene transcription involved interaction of TReP-132 with the transcription factor Sp1 at proximal Sp1-binding sites in their promoters. Moreover, in different breast tumor cell lines, endogenous TReP-132 expression was positively related with a lower proliferation rate. In addition, TReP-132 knockdown resulted in enhanced cell proliferation and lowered p21 and p27 mRNA levels in the steroid-responsive and nonresponsive T-47D and MDA-MB-231 cell lines, respectively. Finally, a statistic profiling of human breast tumor samples highlighted that expression of TReP-132 is correlated with p21 and p27 levels and is associated with lower tumor incidence and aggressiveness. Together, these results identify TReP-132 as a basal cell cycle regulatory protein acting, at least in part, by interacting with Sp1 to activate the p21 and p27 gene promoters.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Cell Cycle / physiology*
  • Cell Cycle Proteins / genetics*
  • Cell Proliferation
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinase Inhibitor p27
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology*
  • Female
  • Gene Expression Regulation
  • Gene Silencing
  • HeLa Cells
  • Humans
  • Promoter Regions, Genetic
  • RNA, Messenger / analysis
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics
  • Sp1 Transcription Factor / metabolism*
  • Steroidogenic Factor 1
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*
  • Tumor Suppressor Proteins / genetics*

Substances

  • CDKN1A protein, human
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p21
  • DNA-Binding Proteins
  • NR5A1 protein, human
  • RNA, Messenger
  • RNA, Small Interfering
  • Sp1 Transcription Factor
  • Steroidogenic Factor 1
  • TRERF1 protein, human
  • Transcription Factors
  • Tumor Suppressor Proteins
  • Cyclin-Dependent Kinase Inhibitor p27