Component of the PeBoW complex, which is required for maturation of 28S and 5.8S ribosomal RNAs and formation of the 60S ribosome. Component of the PeBoW complex, composed of BOP1, PES1 and WDR12. The complex is held together by BOP1, which interacts with PES1 via its N-terminal domain and with WDR12 via a high-affinity interaction between the seven-bladed beta-propeller domains of the 2 proteins. The NOP7 complex associates with the 66S pre-ribosome. The PeBoW complex associates with DDX27, BOP1 interacts directly with DDX27. Belongs to the WD repeat BOP1/ERB1 family.