title: MAD2 depletion triggers premature cellular senescence in human primary fibroblasts by activating a p53 pathway preventing aneuploid cells propagation.
abstract: The spindle assembly checkpoint (SAC) is a cellular surveillance mechanism that ensures faithful chromosome segregation during mitosis and its failure can result in aneuploidy. Previously, it was suggested that reduction of the MAD2 gene, encoding a major component of the SAC, induced aneuploidy in human tumor cells. However, tumor cell lines contain multiple mutations that might affect or exacerbate the cellular response to Mad2 depletion. Thus, the scenario resulting by Mad2 depletion in primary human cells could be different and more complex that the one depicted so far. We used primary human fibroblasts (IMR90) and epithelial breast cells (MCF10A) to gain further insight on the effects of genomic instability caused by transient Mad2 depletion. To this aim we depleted Mad2 by RNAi to a level shown by Mad2 haplo-insufficient cells and found that induced aneuploidy caused premature cellular senescence in IMR90 cells. IMR90 cells showed typical features of senescent cells, like senescence-associated (SA) beta galactosidase expression, including up-regulation of p53 and p14ARF proteins and of p21(waf1) as well, but not of p16(INK4A) cyclin-dependent kinase (Cdk) inhibitor. In contrast, after MAD2 post-transcriptional silencing MCF10A cells in which the INK4A/ARF locus is deleted, showed both aneuploidy and a small increase of p53 and p21(waf1) proteins, but not premature cellular senescence. Finally, our results provides an explanation of how a p53 controlled pathway, involving initially p21(waf1) and then p14ARF, could minimize the occurrence of genomic alterations derived from chromosome instability induced by low amounts of MAD2 protein.
authors.affiliation: Department of Molecular and Biomolecular Science and Technology (STEMBIO) University of Palermo, Palermo, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Lentini
authors.forename: Viviana
authors.initials: V
authors.lastname: Barra
authors.forename: Tiziana
authors.initials: T
authors.lastname: Schillaci
authors.forename: Aldo
authors.initials: A
authors.lastname: Di Leonardo
mesh_terms: D000782:Aneuploidy; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics*; D043171:Chromosomal Instability / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints / Q000235:genetics*; D064246:Mad2 Proteins; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C495901:TP53 protein, human; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D001616:beta-Galactosidase