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

RNA binding is confined to the S1 domain of Rrp5p. IgG Sepharose beads were incubated with extract obtained from cells expressing ProtA-tagged intact Rrp5p (black bar), the TPR domain (ΔS1), or the S1 domain (ΔTPR) and incubated with ³²P-UTP-labeled ITS1 fragment. Binding is expressed relative to the sample containing intact Rrp5p. The white bar represents binding to beads prepared with extract from cells expressing untagged (intact) Rrp5p. (Inset) Western analysis of protein isolated from equal amounts of beads from the three samples.