ATF-a0, a novel variant of the ATF/CREB transcription factor family, forms a dominant transcription inhibitor in ATF-a heterodimers.
We have isolated a cDNA encoding a variant of the transcription factor ATF-a (called ATF-a0) by screening a HeLa cDNA expression library with a regulatory element of the E-selectin promoter, NF-ELAM1/delta A. Relative to full-length ATF-a, the ATF-a0 cDNA contains a large in-frame deletion of 525 base pairs that removes the P/S/T-rich putative transactivation domain. Using reverse-transcription-polymerase chain reaction and Northern blot hybridization to characterize ATF-a0 expression, we found that putative mRNAs for ATF-a0 and ATF-a are present at varying ratios in different tissues. Full-length ATF-a is a transcriptional activator for the NF-ELAM1/delta A site of the E-selectin promoter. In contrast, we show ATF-a0 has no measurable transactivating function on this element. Moreover, we demonstrate that co-expressed ATP-a0 and ATF-a preferentially heterodimerize. In the heterodimer ATF-a0 is a dominant inhibitor that completely blocks the transactivating activity of ATF-a. Both forms of ATF-a bind the p50 subunit of NF-kappa B as shown by affinity chromatography. ATF-a0 appears to be a splice variant similar to the one found for ATF-2, its closest homologue in structure and function. Taken together, our results suggest that ATF-a0 is an important member of the ATF family with a negative regulatory role in transactivation.
Pescini
R
R
GLAXO Institute for Molecular Biology, Geneva, Switzerland.
Kaszubska
W
W
Whelan
J
J
DeLamarter
J F
JF
Hooft van Huijsduijnen
R
R
D051696:Activating Transcription Factors; D000595:Amino Acid Sequence; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics*; D018076:DNA, Complementary; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D051696:Activating Transcription Factors; D001798:Blood Proteins; D018076:DNA, Complementary; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors