HMG box-activating factors 1 and 2, two HMG box transcription factors that bind the human Ig heavy chain enhancer.
We present the isolation of two cDNAs that encode distinct, yet related, proteins that bind the HE2 region of the human Ig heavy chain (IgH) enhancer. Designated HMG box-activating factors (HAF) 1 and 2, the two proteins are new members of the HMG box family of DNA binding proteins. Both are potent transcription activators when expressed 1) as GAL4 fusions targeted to promoters containing GAL4 operators, or 2) as intact proteins targeted to minimal promoters containing binding sites derived from the IgH enhancer. HAF-1 and HAF-2 mRNAs are apparently expressed in both B cells and non-B cells. However, activity generated by the isolated HE2 region in B cells is dependent on both an intact HAF-1/HAF-2 binding site and at least one additional site that has been reported previously to bind a B cell-restricted protein. Our results suggest a collaborative role for either or both HAF-1 and HAF-2 in establishing the B cell activity of the human IgH enhancer.
Stevens
S
S
Department of Genetics and Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Ordentlich
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P
Sen
R
R
Kadesch
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C102078:HAF-1 protein, human; C102079:HAF-2 protein, human; D006609:High Mobility Group Proteins; D007143:Immunoglobulin Heavy Chains; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors