BubR1-and Polo-Coated DNA Tethers Facilitate Poleward Segregation of Acentric Chromatids

Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
Cell (Impact Factor: 32.24). 01/2010; 140(2):235-45. DOI: 10.1016/j.cell.2009.12.043
Source: PubMed


The mechanisms that safeguard cells against chromosomal instability (CIN) are of great interest, as CIN contributes to tumorigenesis. To gain insight into these mechanisms, we studied the behavior of cells entering mitosis with damaged chromosomes. We used the endonuclease I-CreI to generate acentric chromosomes in Drosophila larvae. While I-CreI expression produces acentric chromosomes in the majority of neuronal stem cells, remarkably, it has no effect on adult survival. Our live studies reveal that acentric chromatids segregate efficiently to opposite poles. The acentric chromatid poleward movement is mediated through DNA tethers decorated with BubR1, Polo, INCENP, and Aurora-B. Reduced BubR1 or Polo function results in abnormal segregation of acentric chromatids, a decrease in acentric chromosome tethering, and a great reduction in adult survival. We propose that BubR1 and Polo facilitate the accurate segregation of acentric chromatids by maintaining the integrity of the tethers that connect acentric chromosomes to their centric partners.

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Available from: Roger E Karess, Feb 11, 2014
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    • "e plasma membrane of the cell . Scale bars , 2 μm . ( B ) Still frames from a movie of a dividing neuroblast during the same mitotic stages with I - CreI – induced acentrics decorated with GFP - tagged Aurora B ( cyan arrows ) . Undamaged chromosomes ( cyan arrowheads ) are not associated with Aurora B ( bottom ) . These results are in accord with Royou et al . ( 2010 ) . Dotted lines outline the plasma membrane of the cell . Scale bars , 2 μm . FIGURE 5 : Aurora B RNAi does not lead to gross changes in chromosome behavior or structure . ( A ) Measured size of undamaged chromosomes in I - CreI – expressing control ( cyan triangles ) and I - CreI ; Aurora B RNAi neuroblasts ( red squares ) at the mome"
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    ABSTRACT: To determine how chromosome segregation is coordinated with nuclear envelope formation (NEF), we examined the dynamics of NEF in the presence of lagging acentric chromosomes in Drosophila neuroblasts. Acentric chromosomes often exhibit delayed but ultimately successful segregation and incorporation into daughter nuclei. However, it is unknown whether these late segregating acentric fragments influence NEF to ensure their inclusion in daughter nuclei. Through live analysis, we show that acentric chromosomes induce highly localized delays in the reassembly of the nuclear envelope. These delays result in a gap in the nuclear envelope that facilitates the inclusion of lagging acentrics into telophase daughter nuclei. Localized delays of nuclear envelope reassembly require Aurora B kinase activity. In cells with reduced Aurora B activity, there is a decrease in the frequency of local nuclear envelope reassembly delays, resulting in an increase in the frequency of acentric-bearing lamin-coated micronuclei. These studies reveal a novel role of Aurora B for maintaining genomic integrity by promoting the formation of a passageway in the nuclear envelope through which late segregating acentric chromosomes enter the telophase daughter nucleus. © 2015 by The American Society for Cell Biology.
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    • "Therefore, we next determined if cell elongation associated with the displacement of the spindle toward the GMC affected the localization of cortical myosin, the assembly of the contractile ring, and the rate of the cleavage furrow ingression. To do so, we monitored neuroblasts expressing the nonmuscle myosin II regulatory light chain (encoded by the spaghetti squash gene) " tether, " which transiently increases the length of the chromatid arms during anaphase (Royou et al., 2010). By monitoring Drosophila larval neuroblasts labeled with the histone variant H2Av fused to red fluorescent protein (H2Av::RFP), we found that, after I-CreI expression, the transient increase in chromatid arm length varied considerably between cells, ranging from 1 to nearly 4 times the length of the chromatid mass (Fig. 1 a, cyan arrows; and Fig. 1 c). "
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