OBF1 enhances transcriptional potential of Oct1.
The POU transcription factors Oct1 and Oct2 bind to DNA in various monomer and dimer configurations. Depending on the DNA sequence to which they bind, the dimers are arranged in configurations that are either accessible (PORE sequence) or inaccessible (MORE sequence) to the B-cell-specific cofactor OBF1 (OcaB, Bob1). As shown previously, the MORE and related sequences (such as the heptamer/octamer motif) are found in immunoglobulin heavy chain promoters. Here we show that the expression of Osteopontin, which contains a PORE sequence in its enhancer region, depends on the presence of OBF1 in B cells. OBF1 alleviates DNA sequence requirements of the Oct1 dimer on PORE-related sequences in vitro. Furthermore, OBF1 stabilizes POU dimer-DNA interactions and overrides Oct1 interface mutations, which abolish PORE-mediated dimerization without OBF1. Our data indicate that the PORE-type Oct1 or Oct2 dimer, rather than the monomer, is the primary target of the cofactor OBF1. Based on our biochemical data, we propose a mode of OBF1-Oct1 dimer interaction, suggesting a novel arrangement of the subdomain connectivities.
School of Veterinary Medicine, Department of Animal Biology, University of Pennsylvania, New Bolton Center, Kennett Square, PA 19348, USA.
Katharina
K
Lins
Attila
A
Reményi
Alexey
A
Tomilin
Steffen
S
Massa
Matthias
M
Wilmanns
Patrick
P
Matthias
Hans R
HR
Schöler
D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D019281:Dimerization; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D016297:Mutagenesis, Site-Directed; D027702:Organic Cation Transporter 1 / Q000235:genetics / Q000502:physiology*; D053495:Osteopontin; D050809:POU Domain Factors; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*
D004268:DNA-Binding Proteins; D027702:Organic Cation Transporter 1; D050809:POU Domain Factors; C091546:POU2AF1 protein, human; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D015534:Trans-Activators; D014157:Transcription Factors; D053495:Osteopontin; D004247:DNA