Saccharomyces cerevisiae Ptal is a component of the cleavage/ polyadenylation factor (CPF) 3'-end processing complex and functions in pre-mRNA cleavage, poly(A) addition, and transcription termination. In this study, we investigated the role of the N-terminal region of Ptal in transcription and processing. We report that a deletion of the first 75 amino acids (ptal-Δ75) causes thermosensitive growth, while the deletion of an additional 25 amino acids is lethal. Theptal-Δ75 mutant is defective for snoRNA termination, RNA polymerase II C-terminal domain Ser5-P dephosphorylation, and gene looping but is fully functional for mRNA 3'-end processing. Furthermore, different regions of Ptal interact with the CPF subunits Ssu72, Ptil, and Yshl, supporting the idea that Ptal acts as a scaffold to organize CPF. The first 300 amino acids of Ptal are sufficient for interactions with Ssu72, which is needed for pre-mRNA cleavage. By the degron-mediated depletion of Ptal, we show that the removal of this essential region leads to a loss of Ssu72, yet surprisingly, in vitro cleavage and polyadenylation remain efficient. In addition, a fragment containing amino acids 1 to 300 suppresses 3'-end processing in wild-type extracts. These findings suggest that the amino terminus of Ptal has an inhibitory effect and that this effect can be neutralized through the interaction with Ssu72.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology