FBL is a key small nucleolar protein in eukaryotes, which has an important role in pre-rRNA processing during ribosomal biogenesis. It is associated with the U3, U8, and U13 small nuclear RNAs and is located in the dense fibrillar component (DFC) of the nucleolus. This protein is a component of several ribonucleoproteins including a nucleolar small nuclear ribonucleoprotein (SnRNP) and one of the two classes of small nucleolar ribonucleoproteins (snoRNPs).