The molecular connections between mRNA 3' end processing and transcriptional termination have been investigated in S. pombe using a genetic screen. By this approach, we have identified a RNAP II termination domain in the well-defined cleavage polyadenylation factor called CstF-64 in metazoans and Rna15p in S. cerevisiae. Furthermore, this C-terminal domain interacts with Res2, previously identified as a component of the G1/S transition-specific transcription factor MBF. Deletion of res2 in both fission and budding yeast results in a defect in 3' end formation. This raises the possibility that RNAP II transcriptional termination may in some situations be integrated with cell cycle events.