Differential transactivation potential of Oct1 and Oct2 is determined by additional B cell-specific activities.
Cell type-specific transcriptional regulation is generally believed to be mediated by sequence-specific transcription factors that are specifically present in the corresponding cells. The interaction of the lymphoid-specific Oct2 transcription factor has been thought to be responsible for the B cell-specific activity of octamer-containing promoter and enhancer elements. Here we show that physiological concentrations of Oct2 do not suffice to generate octamer-dependent promoter activity in non-B cell lines. Furthermore, we have tested the activity of octamer-dependent promoter and enhancer elements in B cell lines that lack the endogenous Oct2 protein. Our results demonstrate that in these Oct2-deficient B cells the ubiquitous endogenous Oct1 protein is able to stimulate octamer-containing promoters to a level comparable with that of normal Oct2-positive B cells. However, reporter constructs bearing the octamer motif in a distal enhancer position are not stimulated by the Oct1 protein, but do require the presence of Oct2. The B cell-specific octamer-dependent promoter activity mediated by Oct1 correlates with the presence of a novel B cell-specific octamer-binding complex containing the Oct1 protein. From these results we conclude that B cells contain two different activities: one that interacts with both Oct1 and Oct2 and mediates promoter proximal activity of the octamer motif and a second that specifically interacts with Oct2 to confer function from a remote enhancer position.
Pfisterer
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P
Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
Annweiler
A
A
Ullmer
C
C
Corcoran
L M
LM
Wirth
T
T
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000235:genetics; D051863:Host Cell Factor C1; D051379:Mice; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; C497693:Hcfc1 protein, mouse; D051863:Host Cell Factor C1; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; C494166:Pou2f1 protein, mouse; C489206:Pou2f2 protein, mouse; D014157:Transcription Factors