Abstract

We have used a quantitative fluorescent cDNA microarray hybridization approach to identify pancreatic genes induced by the cellular stress promoted by acute pancreatitis in the mouse. We report the cloning and characterization of one of them that encodes the stress-induced proteins (SIP). The mouse SIP gene is organized into five exons and expands over approximately 20 kilobase pairs. Exon 4 (38 base pairs) is alternatively spliced to generate two transcripts. Northern blot and in situ hybridization showed that both SIP mRNAs are rapidly and strongly induced in acinar cells of the pancreas with acute pancreatitis. They are also constitutively expressed in several other tissues, although with different ratios. They encode proteins of 18 and 27 kDa (SIP(18) and SIP(27)). SIP(27) is identical to the thymus-expressed acidic protein (TEAP) protein, formerly described as a thymus-specific protein. Expression of the SIP(18) and SIP(27)/EGFP or V5 fusion proteins showed that both are nuclear factors. We monitored SIP expression in NIH3T3 cells submitted to various stress agents. UV stress, base damaging, mutagenic stress, ethanol, heat shock, and oxidative stress induced the concomitant expression of SIP(18) and SIP(27) mRNAs. Finally, transient transfection of SIP(18) and SIP(27) expression plasmids induced death by apoptosis in COS7 cells as measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining. In conclusion, the SIP gene is an important element of cellular stress response. It is expressed in many tissues and induced by a variety of stress agents affecting many cellular pathways. SIP generates, by alternative splicing, two nuclear proteins that can promote cell death by apoptosis.

Highlights

  • We have used a quantitative fluorescent cDNA microarray hybridization approach to identify pancreatic genes induced by the cellular stress promoted by acute pancreatitis in the mouse

  • Because the pancreas contains several cell types, we localized stressinduced proteins (SIP) expression by in situ hybridization and found it located to acinar cells only, demonstrating that SIP is involved in the acinar cell response

  • The coding sequences of the two transcripts were identical for the 145 N-terminal amino acids, and the deletion induced a shift in the reading frame resulting in the coding of two proteins of 239- and 163-amino acids that we called SIP27 and SIP18 according to their predicted molecular weight

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Summary

Introduction

We have used a quantitative fluorescent cDNA microarray hybridization approach to identify pancreatic genes induced by the cellular stress promoted by acute pancreatitis in the mouse. Northern blot and in situ hybridization showed that both SIP mRNAs are rapidly and strongly induced in acinar cells of the pancreas with acute pancreatitis. They are constitutively expressed in several other tissues, with different ratios. We and others have previously reported that some genes are strongly activated in pancreatic acinar cells during the acute phase of pancreatitis Most of these genes act to prevent disease evolution, whereas others participate in pancreatic regeneration that follows pancreatitis (reviewed in Ref. 2). We describe the cloning of stress induced protein (SIP), a novel cellular stress-induced gene that generates, by alternative splicing, two nuclear proteins (SIP18 and SIP27) that can induce cell death

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