Basic helix-loop-helix protein E47-mediated p21Waf1/Cip1 gene expression regulates apoptosis of intestinal epithelial cells

Sujoy Bhattacharya, Huazhang Guo, Ramesh M. Ray, Leonard R. Johnson

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Inhibition of ornithine decarboxylase by DFMO (α- difluromethylornithine) and subsequent polyamine depletion increases p21Cip1 protein, induces cell cycle arrest and confers resistance to apoptosis on intestinal epithelial cells. However, the mechanism by which polyamines regulate p21Cip1 expression and apoptosis is unknown. On the basis of the involvement of p21Cip1 as an anti-apoptotic protein, we tested the role of p21Cip1 in providing protection from apoptosis. Simultaneously, we investigated the role of E47, a basic helix-loop-helix protein, in the regulation of p21Cip1 gene transcription. Gene-specific siRNA (small interfering RNA) decreased E47 protein levels, increased p21Cip1 promoter activity and protein levels and protected cells from TNFα (tumour necrosis factor α)-induced apoptosis. Knockdown of p21Cip1 protein by siRNA resulted in cells becoming more susceptible to apoptosis. In contrast, incubation with EGF (epidermal growth factor) stimulated p21Cip1 mRNA and protein levels and rescued cells from apoptosis. During apoptosis, the level of E47 mRNA increased, causing a concomitant decrease in p21Cip1 mRNA and protein levels. Polyamine depletion decreased E47 mRNA levels and cell survival. Caspase 3-mediated cleavage of p130Cas has been implicated in p21Cip1 transcription. The progression of apoptosis led to a caspase 3-dependent cleavage of p130Cas and generated a 31 kDa fragment, which translocated to the nucleus, associated with nuclear E47 and inhibited p21Cip1 transcription. Polyamine depletion inhibited all these effects. Transient expression of the 31 kDa fragment prevented the expression of p21Cip1 protein and increased apoptosis. These results implicate p21Cip1 as an anti-apoptotic protein and suggest a role for poly amines in the regulation of p21Cip1 via the transcription repressor E47. Caspase-mediated cleavage of p130Cas generates a 31 kDa fragment, inhibits p21Cip1 transcription and acts as an amplifier of apoptotic signalling.

Original languageEnglish (US)
Pages (from-to)243-254
Number of pages12
JournalBiochemical Journal
Volume407
Issue number2
DOIs
StatePublished - Oct 15 2007

Fingerprint

Transcription Factor 3
Gene expression
Epithelial Cells
Apoptosis
Gene Expression
Transcription
Polyamines
Proteins
Messenger RNA
Apoptosis Regulatory Proteins
Caspase 3
Small Interfering RNA
Genes
Cell Cycle Proteins
Ornithine Decarboxylase
Caspases
Cell Cycle Checkpoints
Epidermal Growth Factor
Amines
Cell Survival

All Science Journal Classification (ASJC) codes

  • Biochemistry

Cite this

Basic helix-loop-helix protein E47-mediated p21Waf1/Cip1 gene expression regulates apoptosis of intestinal epithelial cells. / Bhattacharya, Sujoy; Guo, Huazhang; Ray, Ramesh M.; Johnson, Leonard R.

In: Biochemical Journal, Vol. 407, No. 2, 15.10.2007, p. 243-254.

Research output: Contribution to journalArticle

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