Induction of Endoplasmic Reticulum-induced Stress Genes in Panc-1 Pancreatic Cancer Cells Is Dependent on Sp Proteins

Maen Abdelrahim,Shengxi Liu,Stephen Safe

doi:10.1074/jbc.c500030200

Abstract

Endoplasmic reticulum (ER) stress plays a critical role in multiple diseases, and pharmacologically active drugs can induce cell death through ER stress pathways. Stress-induced genes are activated through assembly of transcription factors on ER stress response elements (ERSEs) in target gene promoters. Gel mobility shift and chromatin immunoprecipitation assays have confirmed interactions of NF-Y and YY1 with the distal motifs of the tripartite ERSE from the glucose-related protein 78 (GRP78) gene promoter. The GC-rich nonanucleotide (N(9)) sequence, which forms the ER stress response binding factor (ERSF) complex binds TFII-I and ATF6; however, we have now shown that in Panc-1 pancreatic cancer cells, this complex also binds Sp1, Sp3, and Sp4 proteins. Sp proteins are constitutively bound to the ERSE; however, activation of GRP78 protein (or reporter gene) by thapsigargin or tunicamycin is inhibited after cotransfection with small inhibitory RNAs for Sp1, Sp3, and Sp4. This study demonstrates that Sp transcription factors are important for stress-induced responses through their binding to ERSEs.

Highlights

Endoplasmic reticulum (ER) stress plays a critical role in multiple diseases, and pharmacologically active drugs can induce cell death through ER stress pathways
This study demonstrates that activation of the stress response by thapsigargin (Tg) and tunicmycin (Tm) [8, 9, 29, 30] is attenuated by Sp family proteins, and using a combination of gel mobility shift and chromatin immunoprecipitation (ChIP) and transactivation assays, we demonstrate a role for Sp1, Sp3, and Sp4 in mediating ER stress-induced gene expression
ER stress has been linked to various diseases, and several drugs act through activating ER stress pathways, which can lead to growth inhibition and apoptosis [1,2,3,4,5, 13,14,15]

Summary

Introduction

Endoplasmic reticulum (ER) stress plays a critical role in multiple diseases, and pharmacologically active drugs can induce cell death through ER stress pathways. Binds the ER stress response element (ERSE), and the resulting trans-acting protein complex activates expression of several ER stress-responsive genes including glucose-related protein 78 (GRP78) and CHOP (GADD153) [23,24,25,26,27]. The ER stress response element binding factor (ERSF) complex interacts with the ERSE nonanucleotide sequence and contains ATF6 and TFII-I proteins [21, 22, 28]. This study demonstrates that activation of the stress response by thapsigargin (Tg) and tunicmycin (Tm) [8, 9, 29, 30] is attenuated by Sp family proteins, and using a combination of gel mobility shift and chromatin immunoprecipitation (ChIP) and transactivation assays, we demonstrate a role for Sp1, Sp3, and Sp4 in mediating ER stress-induced gene expression

Methods

Results

Conclusion