期刊
BIOCHEMICAL JOURNAL
卷 402, 期 -, 页码 163-173出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20060941
关键词
activating transcription factor; amino acid response element; amino acid transporter; eIF2 phosphorylation; stress response gene; transcriptional regulation
资金
- NCI NIH HHS [R01 CA103867, R01-CA103867] Funding Source: Medline
- NIDDK NIH HHS [R01 DK060596, 5T32-DK07319, R01-DK60596, R01 DK053307, T32 DK007319, R01-DK53307] Funding Source: Medline
The adaptive response to amino acid limitation in mammalian cells inhibits global protein synthesis and promotes the expression of proteins that protect cells from stress. The arginine/lysine transporter, cat-1, is induced during amino acid starvation by transcriptional and post-transcriptional mechanisms. It is shown in the present study that the transient induction of cat-1 transcription is regulated by the stress response pathway that involves phosphorylation of the translation initiation factor, eIF2 (eukaryotic initiation factor-2). This phosphorylation induces expression of the bZIP (basic leucine zipper protein) transcription factors C/ EBP (CCAAT/enhancer-binding protein)-beta and ATF (activating transcription factor) 4, which in turn induces ATF3. Transfection experiments in control and mutant cells, and chromatin immuno-precipitations showed that ATF4 activates, whereas ATF3 represses cat-1 transcription, via an AARE (amino acid response element), TGATGAAAC, in the first exon of the cat-1 gene, which functions both in the endogenous and in a heterologous promoter. ATF4 and C/EBP beta activated transcription when expressed in transfected cells and they bound as heterodimers to the AARE in vitro. The induction of transcription by ATF4 was inhibited by ATF3, which also bound to the AARE as a heterodimer with C/EBP beta. These results suggest that the transient increase in cat-1 transcription is due to transcriptional activation caused by ATF4 followed by transcriptional repression by ATF3 via a feedback mechanism.
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