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

In vivo association of Rrp5p with 5′-extended pre-5.8S RNA species. Extracts were prepared from rrp2-1 cells expressing either untagged Rrp5p (lanes 1,3) or ProtA-Rrp5p (lanes 2,4) and treated with IgG Sepharose beads. Total RNA was isolated from the supernatant (lanes 1,2) and bead (lanes 3,4) fractions and subjected to Northern analysis using probe 3 (cf. Fig. 1) that detects the A2-E and A4-E, 5′-extended pre-5.8S species accumulating in rrp2-1 cells.