Transcription factor that binds to the octamer motif (5'-ATTTGCAT-3'). Forms a trimeric complex with SOX2 or SOX15 on DNA and controls the expression of a number of genes involved in embryonic development such as YES1, FGF4, UTF1 and ZFP206. Critical for early embryogenesis and for embryonic stem cell pluripotency (By similarity). Interacts with PKM. Interacts with WWP2. Interacts with UBE2I and ZSCAN10. Interacts with PCGF1. Interacts with ESRRB; recruits ESRRB near the POU5F1-SOX2 element in the NANOG proximal promoter; the interaction is DNA independent. Interacts with ZNF322. Interacts with MAPK8 and MAPK9; the interaction allows MAPK8 and MAPK9 to phosphorylate POU5F1 on Ser-355. Interacts (when phosphorylated on Ser-355) with FBXW8. Interacts with FBXW4. Interacts with SOX2 and SOX15; binds synergistically with either SOX2 or SOX15 to DNA (By similarity). Expressed in a diffuse and slightly punctuate pattern. Colocalizes with MAPK8 and MAPK9 in the nucleus. The POU-specific domain mediates interaction with PKM. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors. Sumoylation enhances the protein stability, DNA binding and transactivation activity. Sumoylation is required for enhanced YES1 expression. Ubiquitinated; undergoes 'Lys-63'-linked polyubiquitination by WWP2 leading to proteasomal degradation. ERK1/2-mediated phosphorylation at Ser-111 promotes nuclear exclusion and proteasomal degradation. Phosphorylation at Thr-235 and Ser-236 decrease DNA-binding and alters ability to activate transcription. Belongs to the POU transcription factor family. Class-5 subfamily.