title: Replication-compromised cells require the mitotic checkpoint to prevent tetraploidization.
abstract: Replication stress often induces chromosome instability. In this study, we explore which factors in replication-compromised cells promote abnormal chromosome ploidy. We expressed mutant forms of either polymerase α (Polα) or polymerase δ (Polδ) in normal human fibroblasts to compromise DNA replication. Cells expressing the mutant Polα-protein failed to sustain mitotic arrest and, when propagated progressively, down-regulated Mad2 and BubR1 and accumulated 4N-DNA from the 2N-DNA cells. Significantly, a population of these cells became tetraploids. The Polα mutant expressing cells also exhibited elevated cellular senescence markers, suggesting as a mechanism to limit proliferation of the tetraploids. Expression of the Polδ mutant also caused cells to accumulate 4N-DNA. In contrast to the Polα mutant expressing cells, the Polδ mutant expressing cells expressed sufficient levels of Mad2, BubR1, and cyclin B1 to sustain mitotic arrest, and these cells had normal chromosome ploidy. Together, these results suggest that replication-compromised cells depend on the mitotic checkpoint to prevent mitotic slippage that could result in tetraploidization.
authors.affiliation: Department of Pathology, Stanford University Medical Center, Edwards Building, Room R270, 300 Pasteur Drive, Stanford, CA 94305-5324, USA.
authors.forename: Zilai
authors.initials: Z
authors.lastname: Zhang
authors.forename: Sumit
authors.initials: S
authors.lastname: Arora
authors.forename: Yanjiao
authors.initials: Y
authors.lastname: Zhou
authors.forename: Athena
authors.initials: A
authors.lastname: Cherry
authors.forename: Teresa S-F
authors.initials: TS
authors.lastname: Wang
mesh_terms: D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002460:Cell Line; D043171:Chromosomal Instability; D056744:Cyclin B1 / Q000096:biosynthesis / Q000235:genetics; D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D064246:Mad2 Proteins; D008938:Mitosis; D009154:Mutation; D011123:Polyploidy; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: C534699:CCNB1 protein, human; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D056744:Cyclin B1; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D012097:Repressor Proteins; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; D004256:DNA Polymerase I; D019951:DNA Polymerase beta
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