Oct2 transactivation from a remote enhancer position requires a B-cell-restricted activity.
Previous cotransfection experiments had demonstrated that ectopic expression of the lymphocyte-specific transcription factor Oct2 could efficiently activate a promoter containing an octamer motif. Oct2 expression was unable to stimulate a multimerized octamer enhancer element in HeLa cells, however. We have tested a variety of Oct2 isoforms generated by alternative splicing for the capability to activate an octamer enhancer in nonlymphoid cells and a B-cell line. Our analyses show that several Oct2 isoforms can stimulate from a remote position but that this stimulation is restricted to B cells. This result indicates the involvement of either a B-cell-specific cofactor or a specific modification of a cofactor or the Oct2 protein in Oct2-mediated enhancer activation. Mutational analyses indicate that the carboxy-terminal domain of Oct2 is critical for enhancer activation. Moreover, this domain conferred enhancing activity when fused to the Oct1 protein, which by itself was unable to stimulate from a remote position. The glutamine-rich activation domain present in the amino-terminal portion of Oct2 and the POU domain contribute only marginally to the transactivation function from a distal position.
Annweiler
A
A
Zentrum für Molekulare Biologie Heidelberg, Germany.
Müller-Immerglück
M
M
Wirth
T
T
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D006801:Humans; D016350:Leucine Zippers; D008156:Luciferases / Q000096:biosynthesis; D051379:Mice; D008969:Molecular Sequence Data; D050813:Octamer Transcription Factor-2; D012326:RNA Splicing; D011994:Recombinant Proteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D050813:Octamer Transcription Factor-2; C058435:POU2F2 protein, human; C489206:Pou2f2 protein, mouse; D011994:Recombinant Proteins; D014157:Transcription Factors; D008156:Luciferases