Fcf1 (also known as Utp24) is an essential protein involved in pre-rRNA processing and 40S ribosomal subunit assembly []. As a component of the small subunit (SSU) processome, Fcf1 is an essential nucleolar protein required for processing of the 18S pre-rRNA at sites A0-A2 [].The PIN (PilT N terminus) domain is a compact RNA-binding protein domain found in all domains of life. Typically, the PIN domain contains three or four conserved acidic residues (putative metal-binding, active site residues) []. The Fcf1 PIN domain has four of these putative active site residues and the Fcf1-Utp23 homologue PIN domain has three of them. Point mutation studies of the conserved acidic residues in the putative active site of Saccharomyces cerevisiae Fcf1 determined they were essential for pre-rRNA processing at sites A1 and A2, whereas the presence of the Fcf1 protein itself is also required for cleavage at site A0 [, ].
Utp23 share homology with PINc domain protein Fcf1. They are components of the small subunit processome (SSU) that are involved in rRNA-processing and ribosome biogenesis [, ]. Depletion of yeast Fcf1 and Fcf2 leads to a decrease in synthesis of the 18S rRNA and results in a deficit in 40S ribosomal subunits [].
