The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae

Abstract

Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNAbearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny. KEYWORDS Cdc14; Saccharomyces cerevisiae; gross chromosomal rearrangements; aneuploidy; caretaker genes G ENOMIC instability is one of the hallmarks of cancer cells. Many genomic alterations result in gene dose variation including deletions/duplication, gross chromosomal rearrangements (GCRs), and aneuploidy; loss of heterozygosity (LOH) associated with mitotic recombination is also observed (Hanahan and Weinberg 2011). In wild-type cells, specialized mechanisms exist, such as cell cycle checkpoints and DNA repair activities, which suppress genome instability. Genes encoding for proteins that protect cells from cancer-related genomic instability are referred to as caretakers. Many of the tumor suppressor genes identified in familiar cancer-prone syndromes are caretakers. Although caretakers are not directly responsible for the decision of a cell to divide, their loss leads cells to rapidly accumulate genomic aberrations and mutations that potentially result in disorganization of cell division and their subsequent transformation into cancer cells (Kinzler and Vogelstein 1997;van Heemst et al. 2007). For example, mutations in genes involved in DNA repair pathways such as nonhomologous end joining, homologous recombination, mismatch repair, base excision repair, and nucleotide excision repair have been shown to lead to the accumulation of mutations within the genome that significantly increase the risk of carcinogenesis (Negrini et al. 2010; Aguilera and García-Muse 2013 protein (BLM) ac...

Cytological and genetic consequences for the progeny of a mitotic catastrophe provoked by Topoisomerase II deficiency

“…One interpretation of the strong bias for T-LOH events relative to I-LOH events (76 terminal and 3 interstitial) is that DSBs are repaired primarily through BIR (Fig. 5E) [11, 51]. In many previous studies, I-LOH represented a very significant fraction of the total LOH events.…”

The Multiple Roles of the Cdc14 Phosphatase in Cell Cycle Control

“…Similarly, mammalian hCdc14A and hCdc14B are necessary for DNA repair, and their depletion leads to the accumulation of γ-H2AX foci and hypersensitivity to ionizing radiation [91,92]. In S. cerevisiae, inactivation of Cdc14 causes genomic instability and chromosome rearrangements [93]. Furthermore, Cdc14 release from the nucleolus is also stimulated in budding yeast by exposure to different sources of DNA damage, and its activity is essential to restrain cell cycle progression during repair of the lesions [51].…”

Cdc14 phosphatase: warning, no delay allowed for chromosome segregation!

“…The limitations of haploids to assess the putative genomic rearrangements that followed the severing of the cXIIr-AB prompted us to recently study this phenomenon in diploids. Importantly, diploid cells also form the cXIIr-AB, although the failure to timely resolve the bridge after the cdc14 - 1 release is even worse than in haploids (Quevedo et al 2015 ). Also striking is the fact that the viability is even lower despite the existence of additional templates for repair (the chromatids from the other homolog) (Fig.…”

“…It was surprising, though, that chromosomes other than cXII were often rearranged since anaphase bridges involving other chromosomes were less expected. There are many putative causes for these extra rearrangements and we discussed them in detail in the recent manuscript (Quevedo et al 2015 ). In addition to the LOH events on chromosomes other than XII, we observed ploidy alterations.…”

“…The study of Cdc14 has provided important insights into the control of the cell cycle and the counterbalance of CDK activities. Of the many phenotypes observed in cells transiently deficient for Cdc14, the formation of an anaphase bridge that comprises partly resolved sister chromatids has unexpectedly provided a model to study the consequences for the progeny of this aberrant situation (Machín et al 2005 , 2006 ; Quevedo et al 2012 , 2015 ). Anaphase bridges of this nature have long been suspected, and there seems to be a connection with cancer and other human diseases.…”