Cid1, a Fission Yeast Protein Required for S-M Checkpoint Control when DNA Polymerase δ or ɛ Is Inactivated

Abstract

The S-M checkpoint is an intracellular signaling pathway that ensures that mitosis is not initiated in cells undergoing DNA replication. We identified cid1, a novel fission yeast gene, through its ability when overexpressed to confer specific resistance to a combination of hydroxyurea, which inhibits DNA replication, and caffeine, which overrides the S-M checkpoint. Cid1 overexpression also partially suppressed the hydroxyurea sensitivity characteristic of DNA polymerase ␦ mutants and mutants defective in the "checkpoint Rad" pathway. Cid1 is a member of a family of putative nucleotidyltransferases including budding yeast Trf4 and Trf5, and mutation of amino acid residues predicted to be essential for this activity resulted in loss of Cid1 function in vivo. Two additional Cid1-like proteins play similar but nonredundant checkpoint-signaling roles in fission yeast. Cells lacking Cid1 were found to be viable but specifically sensitive to the combination of hydroxyurea and caffeine and to be S-M checkpoint defective in the absence of Cds1. Genetic data suggest that Cid1 acts in association with Crb2/Rhp9 and through the checkpoint-signaling kinase Chk1 to inhibit unscheduled mitosis specifically when DNA polymerase ␦ or is inhibited.

Human DNA Polymerase ε Colocalizes with Proliferating Cell Nuclear Antigen and DNA Replication Late, but Not Early, in S Phase

“…S. pombe pol ⑀ may indirectly participate in the DNA damage response through an interaction with cid1 ϩ . Only cdc20cid1 double mutants, but not either single mutant, show a substantial loss of viability and the appearance of the "cut" phenotype, which indicates aberrant entry into mitosis (36).…”

A regulatory cytoplasmic poly(A) polymerase in Caenorhabditis elegans

“…The similarity between GLD-2 and Cid1 is particularly striking, as both are involved in cell cycle control. GLD-2 promotes entry into meiosis at the expense of mitosis 4 , and Cid1 inhibits mitosis 23 . We suggest that GLD-2 and Cid1 may in fact be components of an ancient regulatory circuit controlling the cell cycle, and that other GLD-2 relatives may similarly be regulatory cytoplasmic PAPs.…”

Terminal Uridyltransferase Enzyme Zcchc11 Promotes Cell Proliferation Independent of Its Uridyltransferase Activity

“…Like Zcchc11, Cid1 is a cytoplasmic uridyltransferase (6,29) that contributes to cell proliferation (7)(8)(9). However, substantial differences do exist.…”

“…Here, we have shown that Zcchc11 promotes G 1 -to-S phase progression, whereas both the yeast and C. elegans Cid1 proteins act primarily in stressed cells to control the G 2 -to-M checkpoint (7)(8)(9). Furthermore, in yeast, the cell cycle regulatory activity of Cid1 is dependent on its uridyltransferase activity, although its uridylation targets have not been identified (8,9). Conversely, we have shown here that the proliferative activity of Zcchc11 is independent of its uridyltransferase domain.…”

“…Therefore, the functions of Zcchc11 are poorly understood at present but have been inferred from its enzymatic activity. Cid1 has been tied to cell cycle progression in both yeast and Caenorhabditis elegans (7)(8)(9). Therefore, one likely role for Zcchc11 is the promotion of cell proliferation.…”