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ATF4 binding to a C/EBP‐ATF composite site is not sufficient to induce endogeneous human System A transporter 2 (SNAT2) transcriptional activation during endoplasmic reticulum stress
Author(s) -
Gjymishka Altin,
Kilberg Michael S.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.306.8
Subject(s) - atf4 , chromatin immunoprecipitation , transcription factor , transcription (linguistics) , unfolded protein response , activating transcription factor 2 , activating transcription factor , microbiology and biotechnology , promoter , biology , endoplasmic reticulum , chemistry , gene , gene expression , biochemistry , linguistics , philosophy
Activation of the amino acid response (AAR) and unfolded protein response (UPR) pathways converge at the phosphorylation of eIF2α, which leads to synthesis of the transcription factor ATF4. The System A amino acid transporter SNAT2 gene contains a C/EBP‐ATF composite site that binds ATF4 and triggers increased transcription during the AAR. Despite increased ATF4 synthesis during the UPR, SNAT2 transcription is not enhanced. This observation leads to the question, is ATF4 binding to the SNAT2 C/EBP‐ATF site sufficient to induce SNAT2 gene transcription? Chromatin immunoprecipitation (ChIP) illustrated that SNAT2 transcription is not induced following UPR activation, despite increased binding of ATF4 to the SNAT2 C/EBP‐ATF site. ChIP analysis also showed that recruitment the general transcription factors to the SNAT2 promoter and hyperacetylation of histone H3 occurs only in response to activation of the AAR but not the UPR. In contrast, the UPR pathway provoked enhanced SNAT2 transcription from a plasmid‐based luciferase reporter driven by a SNAT2 fragment containing the C/EBP‐ATF composite sequence and mutation of the sequence abolished the induction. The results demonstrate that ATF4 binding alone is not sufficient to illicit enhanced transcription and that parallel changes in chromatin structure are necessary as well. Funded by grants from the NIH (DK‐52064, DK‐70647).