Transcriptional coactivator that specifically associates with either POU2F1/OCT1 or POU2F2/OCT2 (PubMed:7859290). It boosts the POU2F1/OCT1 mediated promoter activity and to a lesser extent, that of POU2F2/OCT2 (PubMed:7779176). It has no intrinsic DNA-binding activity. It recognizes the POU domains of POU2F1/OCT1 and POU2F2/OCT2 (PubMed:7779176). It is essential for the response of B-cells to antigens and required for the formation of germinal centers (PubMed:7623806, PubMed:7859290). Regulates IL6 expression in B cells as POU2F2/OCT2 coactivator (By similarity). Interacts with POU2F1/OCT1 and POU2F2/OCT2; the interaction increases POU2F1 and POU2F2 transactivation activity. B-cell specific (PubMed:7779176, PubMed:7859290). Detected in mainly in spleen, but also in thymus, periphral blood leukocyte and small intestine (PubMed:7779176, PubMed:7859290). Ubiquitinated; mediated by SIAH1 or SIAH2 and leading to its subsequent proteasomal degradation. A chromosomal aberration involving POU2AF1/OBF1 may be a cause of a form of B-cell leukemia. Translocation t(3;11)(q27;q23) with BCL6. Belongs to the POU2AF1 family.