C/EBP Homology Protein (CHOP) Interacts with Activating Transcription Factor 4 (ATF4) and Negatively Regulates the Stress-dependent Induction of the Asparagine Synthetase Gene
C/EBP Homology Protein (CHOP) Interacts with Activating Transcription Factor 4 (ATF4) and Negatively Regulates the Stress-dependent Induction of the Asparagine Synthetase Gene
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DOI：
10.1074/jbc.m806874200
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发表时间：
2008-12-12
影响因子：
4.8
通讯作者：
Kilberg, Michael S.
中科院分区：
文献类型：
--
作者：
Su, Nan;Kilberg, Michael S.
C/EBP同源蛋白（CHOP）是一种应激诱导的转录因子，参与转录调控、细胞周期和凋亡。本研究在酵母双杂交筛选中将CHOP鉴定为转录激活因子（ATF）4的相互作用伴侣，并证实了它们在HEK 293 T细胞中的相互作用。CHOP蛋白水平上升温和和短暂的氨基酸剥夺，而内质网应激引起了更高的和持续的表达CHOP蛋白。外源CHOP表达增强了TRB 3基因诱导的氨基酸剥夺。相反，CHOP抑制了内源性天冬酰胺合成酶（ASNS）基因的诱导，并抑制了ATF 4激活或氨基酸剥夺后由ASNS启动子驱动的报告基因的转录。短干扰RNA介导的敲低CHOP进一步增强了由氨基酸剥夺或内质网应激引起的ASNS诱导。ASNS基因的CHOP依赖性抑制需要整个CHOP蛋白，反对CHOP亮氨酸拉链结构域简单隔离ATF 4的可能性，染色质免疫沉淀分析显示CHOP与ASNS和TRB 3启动子相关。有趣的是，染色质免疫沉淀也显示CHOP与SNAT 2、VEGF和CAT-1基因的C/EBP-ATF复合位点区域相关，尽管外源性CHOP过表达后对其表达无显著影响。总的来说，这些结果证明CHOP是转录因子网络的一员，该网络控制着特定C/EBP-ATF基因（如ASNS）的应激诱导调控。
C/EBP homology protein (CHOP), a stress-induced transcription factor, is involved in transcriptional regulation, cell cycle, and apoptosis. The present studies identified CHOP as an interacting partner of activating transcription factor (ATF) 4 in a yeast two-hybrid screen and confirmed their interaction in HEK293T cells. CHOP protein levels rose modestly and transiently during amino acid deprivation, whereas endoplasmic reticulum stress caused a much higher and sustained expression of CHOP protein. Exogenous CHOP expression enhanced the TRB3 gene induction by amino acid deprivation. Conversely, CHOP suppressed the induction of the endogenous asparagine synthetase (ASNS) gene and inhibited transcription from a reporter gene driven by the ASNS promoter following activation by ATF4 or amino acid deprivation. Short interfering RNA-mediated knockdown of CHOP further enhanced the induction of ASNS by either amino acid deprivation or endoplasmic reticulum stress. The CHOP-dependent repression of the ASNS gene required the entire CHOP protein, arguing against the possibility of simple sequestration of ATF4 by the CHOP leucine zipper domain, and chromatin immunoprecipitation analysis showed association of CHOP with the ASNS and TRB3 promoters. Interestingly, chromatin immunoprecipitation also showed that CHOP was associated with the C/EBP-ATF composite site regions of the SNAT2, VEGF, and CAT-1 genes, despite no significant effect on their expression after exogenous CHOP overexpression. Collectively, the results document that CHOP is a member of the transcription factor network that controls the stress-induced regulation of specific C/EBP-ATF-containing genes, such as ASNS.