Stimulation of basal transcription from the mouse mammary tumor virus promoter by Oct proteins.
The steroid hormone-inducible promoter of mouse mammary tumor virus (MMTV) contains three overlapping sequences related to the consensus octamer motif ATGCAAAT. Basal promoter activity in the absence of hormone induction from a template in which all three octamer elements were mutated was decreased by two-to threefold in in vitro transcription assays. Oct-1 protein purified from HeLa cell nuclear extracts, as well as recombinant Oct-1 expressed in bacteria, recognized MMTV octamer-related sequences, as shown by DNase I footprinting. Furthermore, rabbit polyclonal antiserum directed against recombinant Oct-1 completely inhibited the formation of specific complexes between MMTV octamer-related sequences and proteins present in nuclear extracts of HeLa cells, indicating that Oct-1 is the major protein in HeLa nuclear extracts that recognizes octamer-related sequences in the MMTV promoter. In addition, depletion of Oct-1 from the nuclear extract by using Oct-1-specific antiserum or a sequence-specific DNA affinity resin decreased in vitro transcription from the wild-type MMTV promoter to a level identical to that obtained from a promoter in which all three octamer-related sequences were mutated. Addition of purified HeLa Oct-1 or recombinant Oct-1 to the depleted extract selectively increased transcription from the wild-type relative to the mutated promoter, demonstrating that Oct-1 transcription factor stimulates basal transcription from the MMTV promoter. A similar effect was observed when purified recombinant Oct-2 was added to the Oct-1-depleted extract, suggesting that Oct-2 may play an important role in MMTV transcription in B cells.
Kim
M H
MH
Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA.
Peterson
D O
DO
D001483:Base Sequence; D002846:Chromatography, Affinity; D004279:DNA, Viral; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D006367:HeLa Cells; D051863:Host Cell Factor C1; D006801:Humans; D007106:Immune Sera; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D014157:Transcription Factors / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*
D004279:DNA, Viral; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D007106:Immune Sera; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; C489206:Pou2f2 protein, mouse; D011994:Recombinant Proteins; D014157:Transcription Factors