Oct-2 facilitates functional preinitiation complex assembly and is continuously required at the promoter for multiple rounds of transcription.
Octamer factor 2 (Oct-2, OTF-2, NF-A2) is an 'upstream' promoter factor that binds to the octamer motif (ATGCAAAT) implicated in control of immunoglobulin gene transcription in B-lymphocytes. We have studied the role of Oct-2 in the process of transcription initiation in vitro using both nuclear extracts and purified basal transcription factors. Oct-2 specifically stimulates transcription from octamer-containing promoters in both systems. Thus, Oct-2 is a 'true activator', rather than merely an 'anti-repressor' counteracting the effect of histones. In order-of-addition experiments, Oct-2 is required early, together with TFIID, to allow formation of a preinitiation complex. Oct-2 cannot functionally interact with cloned TATA binding protein (TBP) but rather requires 'coactivators' found in the TFIID fraction. In single-round transcription experiments, early competition for Oct-2 by an octamer oligonucleotide is deleterious, but no effect is seen after assembly of a complete preinitiation complex. However, for multiple rounds of transcription, Oct-2 is continuously required at the promoter; this result argues against a 'hit-and-run' mechanism whereby the activator becomes dispensible after organizing a TFIID-promoter complex. In agreement with our previous studies in vivo, the N-terminal glutamine-rich activation domain of Oct-2 is required for full activity in vitro, indicating that this domain directly interacts with basal transcription factors.
Arnosti
D N
DN
Institute of Molecular Biology II, University of Zürich, Switzerland.
Merino
A
A
Reinberg
D
D
Schaffner
W
W
D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000378:metabolism*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D019474:Transcription Factors, TFIII; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; C058435:POU2F2 protein, human; D011994:Recombinant Proteins; D014157:Transcription Factors; D019474:Transcription Factors, TFIII; C053256:transcription factor TFIIID