Rrp5p, a trans-acting factor in yeast ribosome biogenesis, is an RNA-binding protein with a pronounced preference for U-rich sequences

Competition binding experiments using homopolymers. ProtA-Rrp5p-loaded beads were incubated with ³²P-UTP-labeled ITS1 fragment in the absence or the presence of excess homopolymer as indicated. Either single-stranded (dark gray bars) or (mock-) annealed (light gray bars) homopolymer was used as competitor. Binding is expressed relative to the sample containing no competitor. The white bar represents binding to control beads prepared with extract from cells expressing untagged Rrp5p.