Inactivation of the Pre-mRNA Cleavage and Polyadenylation Factor Pfs2 in Fission Yeast Causes Lethal Cell Cycle Defects

Abstract

Faithful chromosome segregation is fundamentally important for the maintenance of genome integrity and ploidy. By isolating conditional mutants defective in chromosome segregation in the fission yeast Schizosaccharomyces pombe, we identified a role for the essential gene pfs2 in chromosome dynamics. In the absence of functional Pfs2, chromosomal attachment to the mitotic spindle was defective, with consequent chromosome missegregation. Under these circumstances, multiple intracellular foci of spindle checkpoint proteins Bub1 and Mad2 were seen, and deletion of bub1 exacerbated the mitotic defects and the loss of cell viability that resulted from the loss of pfs2 function. Progression from G₁ into S phase following release from nitrogen starvation also required pfs2⁺ function. The product of the orthologous Saccharomyces cerevisiae gene PFS2 is a component of a multiprotein complex required for 3′-end cleavage and polyadenylation of pre-mRNAs and, in keeping with the conservation of this essential function, an S. pombe pfs2 mutant was defective in mRNA 3′-end processing. Mutations in pfs2 were suppressed by overexpression of the putative mRNA 3′-end cleavage factor Cft1. These data suggest unexpected links between mRNA 3′-end processing and chromosome replication and segregation.

ACKNOWLEDGMENTS

We are grateful to Nick Proudfoot and members of his group for valuable discussions, to Paul Russell for bringing our attention to the reannotation of the pfs2 and cid14 genes, to Stephen Kearsey for comments on the manuscript, to Jean-Paul Javerzat for providing the bub1 deletion strain, and to Taro Nakamura and Chikashi Shimoda for providing the genomic DNA library.

This work was supported by Cancer Research UK, the Human Frontiers Science Program (research grant to T.T.), the Association for International Cancer Research, and the Wellcome Trust (research career development award to S.-W.W.).