title: Elevated levels of the polo kinase Cdc5 override the Mec1/ATR checkpoint in budding yeast by acting at different steps of the signaling pathway.
abstract: Checkpoints are surveillance mechanisms that constitute a barrier to oncogenesis by preserving genome integrity. Loss of checkpoint function is an early event in tumorigenesis. Polo kinases (Plks) are fundamental regulators of cell cycle progression in all eukaryotes and are frequently overexpressed in tumors. Through their polo box domain, Plks target multiple substrates previously phosphorylated by CDKs and MAPKs. In response to DNA damage, Plks are temporally inhibited in order to maintain the checkpoint-dependent cell cycle block while their activity is required to silence the checkpoint response and resume cell cycle progression. Here, we report that, in budding yeast, overproduction of the Cdc5 polo kinase overrides the checkpoint signaling induced by double strand DNA breaks (DSBs), preventing the phosphorylation of several Mec1/ATR targets, including Ddc2/ATRIP, the checkpoint mediator Rad9, and the transducer kinase Rad53/CHK2. We also show that high levels of Cdc5 slow down DSB processing in a Rad9-dependent manner, but do not prevent the binding of checkpoint factors to a single DSB. Finally, we provide evidence that Sae2, the functional ortholog of human CtIP, which regulates DSB processing and inhibits checkpoint signaling, is regulated by Cdc5. We propose that Cdc5 interferes with the checkpoint response to DSBs acting at multiple levels in the signal transduction pathway and at an early step required to resect DSB ends.
authors.affiliation: Dipartimento di Scienze Biomolecolari e Biotecnologie, Universita' degli Studi di Milano, Milano, Italy.
authors.forename: Roberto Antonio
authors.initials: RA
authors.lastname: Donnianni
authors.forename: Matteo
authors.initials: M
authors.lastname: Ferrari
authors.forename: Federico
authors.initials: F
authors.lastname: Lazzaro
authors.forename: Michela
authors.initials: M
authors.lastname: Clerici
authors.forename: Benjamin
authors.initials: B
authors.lastname: Tamilselvan Nachimuthu
authors.forename: Paolo
authors.initials: P
authors.lastname: Plevani
authors.forename: Marco
authors.initials: M
authors.lastname: Muzi-Falconi
authors.forename: Achille
authors.initials: A
authors.lastname: Pellicioli
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D048750:Cell Nucleus Division; D064447:Checkpoint Kinase 2; D053903:DNA Breaks, Double-Stranded; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C081927:CDC5 protein, S cerevisiae; C067022:RAD53 protein, S cerevisiae