Transcriptional coactivator that specifically associates with either POU2F1/OCT1 or POU2F2/OCT2. It boosts the POU2F1/OCT1 mediated promoter activity and to a lesser extent, that of POU2F2/OCT2. It has no intrinsic DNA-binding activity. It recognizes the POU domains of POU2F1/OCT1 and POU2F2/OCT2. It is essential for the response of B-cells to antigens and required for the formation of germinal centers. Regulates IL6 expression in B cells as POU2F2/OCT2 coactivator. Interacts with POU2F1/OCT1 and POU2F2/OCT2; the interaction increases POU2F1 and POU2F2 transactivation activity. Ubiquitinated; mediated by SIAH1 or SIAH2 and leading to its subsequent proteasomal degradation. Belongs to the POU2AF1 family.