Transcription factor that binds to the octamer motif (5'-ATTTGCAT-3') and activates the promoters of the genes for some small nuclear RNAs (snRNA) and of genes such as those for histone H2B and immunoglobulins. Modulates transcription transactivation by NR3C1, AR and PGR. (Microbial infection) In case of human herpes simplex virus (HSV) infection, POU2F1 forms a multiprotein-DNA complex with the viral transactivator protein VP16 and HCFC1 thereby enabling the transcription of the viral immediate early genes. Interacts with POU2AF1; the interaction increases POU2F1 transactivation activity (PubMed:7859290). Interacts with NR3C1, AR, PGR and HCFC1. (Microbial infection) Associates with the herpes simplex virus VP16-induced complex; binding to HCFC1 activates the viral transcriptional activator VP16 for association with POU2F1, to form a multiprotein-DNA complex responsible for activating transcription of the viral immediate early genes. Ubiquitous. Isoform 2 is lymphocyte-specific. Phosphorylated by PRKDC. Belongs to the POU transcription factor family. Class-2 subfamily.