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 PeBoW complex associates with the 66S pre-ribosome. Widely and highly expressed during the first 3 days of embryogenesis. Prominent sites of expression are the eyes and optic tectum on day 1, the fin buds, liver primordium, and gut on day 2, and the branchial arches on day 3. Embryos exhibit smaller eyes, a reduced brain and visceral skeleton, shortened fins and a lack of expansion of liver and gut, and die on day 6 of development. Belongs to the pescadillo family.