Eukaryotic RNA polymerase II transcribes precursors of mRNAs and of 
non-protein-coding RNAs such as snRNAs and snoRNAs. These RNAs have to be 
processed at their 3' ends to be functional. mRNAs are matured by cleavage and 
polyadenylation that require a well-characterized protein complex. Small RNAs 
are also subject to 3' end cleavage but are not polyadenylated. Here we show 
that two newly identified proteins, Pti1p and Ref2p, although they were found 
associated with the pre-mRNA 3' end processing complex, are essential for yeast 
snoRNA 3' end maturation. We also provide evidence that Pti1p probably acts by 
uncoupling cleavage and polyadenylation, and functions in coordination with the 
Nrd1p-dependent pathway for 3' end formation of non-polyadenylated transcripts.