Cwc24p, a novel S. cerevisiae RING‐finger protein, affects U3 snoRNA splicing and rRNA processing

Abstract

Ribosome biogenesis involve the extensive processing of a precursor rRNA 35S by approximately 150 trans‐acting factors, giving rise to the mature rRNAs. Among these factors are snoRNPs (small nucleolar ribonucleoproteins), that are formed by a guide snoRNA (that base‐pairs with target sites within the pre‐rRNA) and evolutionarily conserved proteins. In this work we present the functional characterization of Cwc24p, a novel S. cerevisiae RING‐finger that interacts with Nop17p (a box C/D snoRNP assembly factor) and with Cef1p (a splicing factor, component of the NTC complex). Consistent with the interaction data, Cwc24p localizes to the cell nucleus. Using a conditional strain (GAL1::CWC24) we observed a small defect in rRNA processing upon depletion of Cwc24p. In order to investigate the involvement of Cwc24p in splicing, a splicing‐specific microarray analysis was conducted and revealed that depletion of Cwc24p leads to the accumulation of both U3 pre‐snoRNAs. U3 snoRNA, which is transcribed from two intron‐containing genes in yeast, is involved in the early cleavages of 35S pre‐rRNA, and the defective splicing of pre‐U3 detected in cells depleted of Cwc24p may be responsible for the accumulation of the 35S precursor rRNA. These results led us to the conclusion that Cwc24p is involved in pre‐U3 snoRNA splicing, indirectly affecting pre‐rRNA processing.Supported by FAPESP and CAPES