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Gene Review

POU2AF1  -  POU class 2 associating factor 1

Homo sapiens

Synonyms: B-cell-specific coactivator OBF-1, BOB-1, BOB1, OBF-1, OBF1, ...
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Disease relevance of POU2AF1


High impact information on POU2AF1

  • An interaction with OBF-1 is precluded since the same Oct-1 residues that form the MORE dimerization interface are also used for OBF-1/Oct-1 interactions on the PORE [5].
  • The OBF-1 mRNA is expressed in a highly cell-specific manner, being most abundant in B cells and essentially absent in most of the other cells or tissues tested [6].
  • Using a genetic screen in yeast, we have isolated B cell-derived cDNAs encoding Oct-binding factor 1 (OBF-1), a novel protein that specifically associates with Oct-1 and Oct-2 [6].
  • Furthermore, expression of OBF-1 in HeLa cells selectively stimulates the activity of a natural immunoglobulin promoter in an octamer site-dependent manner [6].
  • The OCA-B peptide binds in the major groove near the center of the octamer site, and its polypeptide backbone forms a pair of hydrogen bonds with the adenine base at position 5 of the octamer DNA [7].

Biological context of POU2AF1

  • POU2AF1 is a B-cell-specific transcriptional coactivator, and BTG4 is a member of the BTG family of negative regulators of the cell cycle, making both of them good candidate genes for the pathogenesis of 11q- CLL [1].
  • 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 [8].
  • 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) [8].
  • Furthermore, OBF1 stabilizes POU dimer-DNA interactions and overrides Oct1 interface mutations, which abolish PORE-mediated dimerization without OBF1 [8].
  • Bob1 transactivation only occurs with select octamer sequences that have an adenosine at position 5 (ATGCAAAT) [9].

Anatomical context of POU2AF1

  • POU2AF1 was observed to be differentially expressed in the cells of patients with CLL compared to its expression in normal B cells in the absence of mutations [1].
  • The transcriptional coactivator OBF-1, which interacts with Oct-1 and Oct-2 and the octamer site DNA, has been shown to be critical for development of a normal immune response and the formation of germinal centers in secondary lymphoid organs [10].
  • Further analysis of general coactivator requirements showed that selective removal of PC4 from the essential USA fraction severely impairs Oct-1 and OCA-B function in a cell-free system reconstituted with partially purified factors [11].
  • However, the high frequency of BOB-1 expression in T-cell neoplasms, in contrast to its absence from resting peripheral T cells, suggests that its expression might be a prerequisite for neoplastic transformation, and prompts a search for the transcriptional target(s) of this factor in T cells [3].
  • During B cell development OBF-1 expression shows two peaks, one in immature B cells in the bone marrow and the other in germinal center B cells [12].

Associations of POU2AF1 with chemical compounds

  • Nucleotidic sequence of a nearly full-length cDNA of the BOB1/OBF1 gene revealed particular features in the 3' untranslated region of the gene, including pyrimidine-rich sequence repeats, an Alu motif, and a polymorphic [CCTT] tetranucleotide microsatellite [13].

Physical interactions of POU2AF1

  • Here we have identified the RING finger protein Siah-1 as a protein interacting specifically with OBF-1 [10].
  • In pull-down assays, increasing amounts of SMRT could compete the binding of OCA-B to Oct-1 POU domain [14].

Regulatory relationships of POU2AF1

  • The RING finger protein Siah-1 regulates the level of the transcriptional coactivator OBF-1 [10].

Other interactions of POU2AF1

  • Based on our biochemical data, we propose a mode of OBF1-Oct1 dimer interaction, suggesting a novel arrangement of the subdomain connectivities [8].
  • These findings indicate that genomic imbalances or rearrangements are not a cause of PU.1, BOB1, and OCT2 deficiency in cHL and argue for another mechanism underlying this phenomenon [15].
  • This interaction is mediated by the C-terminal part of Siah-1 and by residues in the N-terminus of OBF-1, partly distinct from the residues required for formation of a complex with the Oct POU domains and the DNA [10].
  • The lymphoid-specific transcriptional coactivator OBF-1 (also known as OCA-B or Bob-1) is recruited to octamer site-containing promoters by interacting with Oct-1 or Oct-2 and thereby enhances the transactivation potential of these two Oct factors [16].
  • The activity of Oct-1 could be determined by a regulated balance between SMRT and OCA-B [14].

Analytical, diagnostic and therapeutic context of POU2AF1

  • Molecular dissection of the B-cell-specific transcription coactivator OCA-B has revealed distinct regions important, respectively, for recruitment to immunoglobulin promoters through interaction with octamer-bound Oct-1 and for subsequent coactivator function [11].
  • By methylation interference analysis we identified bases that react differently in the presence of OBF-1 compared to the POU domain alone, and using phosphothioate backbone-modified probes in electrophoretic mobility shift assays, we identified several positions influencing ternary complex formation [16].
  • Assignment of the human gene for Oct-binding factor-1 (OBF1), a B-cell-specific coactivator of octamer-binding transcription factors 1 and 2, to 11q23.1 by somatic cell hybridization and in situ hybridization [17].
  • Using microarray analysis, we have identified the Ets transcription factor Spi-B as a direct target gene critically regulated by OBF-1 that can help explain the phenotype of OBF-1-deficient mice [18].
  • In addition, the presence of hAd did not significantly modify the AP activity of hBOB (0.163 +/- 0.143 and 0.181 +/- 0.114 nmol/min per microgram of protein in controls and after coculture, respectively) [19].


  1. Identification of a potential role for POU2AF1 and BTG4 in the deletion of 11q23 in chronic lymphocytic leukemia. Auer, R.L., Starczynski, J., McElwaine, S., Bertoni, F., Newland, A.C., Fegan, C.D., Cotter, F.E. Genes Chromosomes Cancer (2005) [Pubmed]
  2. Linkage disequilibrium screening for multiple sclerosis implicates JAG1 and POU2AF1 as susceptibility genes in Europeans. The Games Collaborative Group, n.u.l.l. J. Neuroimmunol. (2006) [Pubmed]
  3. Expression of B-lymphocyte-associated transcription factors in human T-cell neoplasms. Marafioti, T., Ascani, S., Pulford, K., Sabattini, E., Piccioli, M., Jones, M., Zinzani, P.L., Delsol, G., Mason, D.Y., Pileri, S.A. Am. J. Pathol. (2003) [Pubmed]
  4. OCA-B is a functional analog of VP16 but targets a separate surface of the Oct-1 POU domain. Babb, R., Cleary, M.A., Herr, W. Mol. Cell. Biol. (1997) [Pubmed]
  5. Synergism with the coactivator OBF-1 (OCA-B, BOB-1) is mediated by a specific POU dimer configuration. Tomilin, A., Reményi, A., Lins, K., Bak, H., Leidel, S., Vriend, G., Wilmanns, M., Schöler, H.R. Cell (2000) [Pubmed]
  6. OBF-1, a novel B cell-specific coactivator that stimulates immunoglobulin promoter activity through association with octamer-binding proteins. Strubin, M., Newell, J.W., Matthias, P. Cell (1995) [Pubmed]
  7. Crystal structure of an OCA-B peptide bound to an Oct-1 POU domain/octamer DNA complex: specific recognition of a protein-DNA interface. Chasman, D., Cepek, K., Sharp, P.A., Pabo, C.O. Genes Dev. (1999) [Pubmed]
  8. OBF1 enhances transcriptional potential of Oct1. Lins, K., Reményi, A., Tomilin, A., Massa, S., Wilmanns, M., Matthias, P., Schöler, H.R. EMBO J. (2003) [Pubmed]
  9. Bob1 (OCA-B/OBF-1) differential transactivation of the B cell-specific B29 (Ig beta) and mb-1 (Ig alpha) promoters. Malone, C.S., Wall, R. J. Immunol. (2002) [Pubmed]
  10. The RING finger protein Siah-1 regulates the level of the transcriptional coactivator OBF-1. Tiedt, R., Bartholdy, B.A., Matthias, G., Newell, J.W., Matthias, P. EMBO J. (2001) [Pubmed]
  11. Coactivation by OCA-B: definition of critical regions and synergism with general cofactors. Luo, Y., Ge, H., Stevens, S., Xiao, H., Roeder, R.G. Mol. Cell. Biol. (1998) [Pubmed]
  12. The OBF-1 gene locus confers B cell-specific transcription by restricting the ubiquitous activity of its promoter. Massa, S., Junker, S., Schubart, K., Matthias, G., Matthias, P. Eur. J. Immunol. (2003) [Pubmed]
  13. Fusion of the LAZ3/BCL6 and BOB1/OBF1 genes by t(3; 11) (q27; q23) chromosomal translocation. Galiègue-Zouitina, S., Quief, S., Hildebrand, M.P., Denis, C., Lecocq, G., Collyn-d'Hooghe, M., Bastard, C., Yuille, M., Dyer, M.J., Kerckaert, J.P. C. R. Acad. Sci. III, Sci. Vie (1995) [Pubmed]
  14. Silencing mediator for retinoid and thyroid hormone receptors interacts with octamer transcription factor-1 and acts as a transcriptional repressor. Kakizawa, T., Miyamoto, T., Ichikawa, K., Takeda, T., Suzuki, S., Mori , J., Kumagai, M., Yamashita, K., Hashizume, K. J. Biol. Chem. (2001) [Pubmed]
  15. Alterations of loci encoding PU.1, BOB1, and OCT2 transcription regulators do not correlate with their suppressed expression in Hodgkin lymphoma. Cavazzini, F., De Wolf-Peeters, C., Wlodarska, I. Cancer Genet. Cytogenet. (2005) [Pubmed]
  16. Coactivator OBF-1 makes selective contacts with both the POU-specific domain and the POU homeodomain and acts as a molecular clamp on DNA. Sauter, P., Matthias, P. Mol. Cell. Biol. (1998) [Pubmed]
  17. Assignment of the human gene for Oct-binding factor-1 (OBF1), a B-cell-specific coactivator of octamer-binding transcription factors 1 and 2, to 11q23.1 by somatic cell hybridization and in situ hybridization. Junker, S., Brøndum-Nielsen, K., Newell, J.W., Matthias, P., Tommerup, N. Genomics (1996) [Pubmed]
  18. The Ets factor Spi-B is a direct critical target of the coactivator OBF-1. Bartholdy, B., Du Roure, C., Bordon, A., Emslie, D., Corcoran, L.M., Matthias, P. Proc. Natl. Acad. Sci. U.S.A. (2006) [Pubmed]
  19. Influence of mature adipocytes on osteoblast proliferation in human primary cocultures. Maurin, A.C., Chavassieux, P.M., Frappart, L., Delmas, P.D., Serre, C.M., Meunier, P.J. Bone (2000) [Pubmed]
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