Stress-induced binding of the transcriptional factor CHOP to a novel DNA control element.
CHOP (GADD153) is a mammalian nuclear protein that dimerizes with members of the C/EBP family of transcriptional factors. Absent under normal conditions, CHOP is induced by the stress encountered during nutrient deprivation, the acute-phase response, and treatment of cells with certain toxins. The basic region of CHOP deviates considerably in sequence from that of other C/EBP proteins, and CHOP-C/EBP heterodimers are incapable of binding to a common class of C/EBP sites. With respect to such sites, CHOP serves as an inhibitor of the activity of C/EBP proteins. However, recent studies indicate that certain functions of CHOP, such as the induction of growth arrest by overexpression of the wild-type protein and oncogenic transformation by the TLS-CHOP fusion protein, require an intact basic region, suggesting that DNA binding by CHOP may be implicated in these activities. In this study an in vitro PCR-based selection assay was used to identify sequences bound by CHOP-C/EBP dimers. These sequences were found to contain a unique core element PuPuPuTGCAAT(A/C)CCC. Competition in DNA-binding assays, DNase 1 footprint analysis, and methylation interference demonstrate that the binding is sequence specific. Deletions in the basic region of CHOP lead to a loss of DNA binding, suggesting that CHOP participates in this process. Stress induction in NIH 3T3 cells leads to the appearance of CHOP-containing DNA-binding activity. CHOP is found to contain a transcriptional activation domain which is inducible by cellular stress, lending further support to the notion that the protein can function as a positively acting transcription factor. We conclude that CHOP may serve a dual role both as an inhibitor of the ability of C/EBP proteins to activate some target genes and as a direct activator of others.
Ubeda
M
M
Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Wang
X Z
XZ
Zinszner
H
H
Wu
I
I
Habener
J F
JF
Ron
D
D
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D003850:Deoxyribonuclease I; D018257:Helix-Loop-Helix Motifs; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D017384:Sequence Deletion; D015534:Trans-Activators / Q000096:biosynthesis / Q000378:metabolism; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*
C085848:C-EBP nuclear protein trans-activation element II; D022763:CCAAT-Enhancer-Binding Protein-alpha; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; C497250:Ddit3 protein, mouse; C497251:Ddit3 protein, rat; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051742:Transcription Factor CHOP; D003850:Deoxyribonuclease I