Abstract
BackgroundProper regulation of the cohesion at the centromeres of human chromosomes is essential for accurate genome transmission. Exactly how cohesion is maintained and is then dissolved in anaphase is not understood.Principal FindingsWe have investigated the role of the cohesin complex at centromeres in human cells both by depleting cohesin subunits using RNA interference and also by expressing a non-cleavable version of the Rad21 cohesin protein. Rad21 depletion results in aberrant anaphase, during which the sister chromatids separate and segregate in an asynchronous fashion. However, centromere cohesion was maintained before anaphase in Rad21-depleted cells, and the primary constrictions at centromeres were indistinguishable from those in control cells. Expression of non-cleavable Rad21 (NC-Rad21), in which the sites normally cleaved by separase are mutated, resulted in delayed sister chromatid resolution in prophase and prometaphase, and a blockage of chromosome arm separation in anaphase, but did not impede centromere separation.ConclusionsThese data indicate that cohesin complexes are dispensable for sister cohesion in early mitosis, yet play an important part in the fidelity of sister separation and segregation during anaphase. Cleavage at the separase-sensitive sites of Rad21 is important for arm separation, but not for centromere separation.
Highlights
Faithful chromosome segregation requires that sister DNA molecules remain attached to one another until anaphase
Similar phenotypes are observed in vivo in mouse hepatocytes, and in tissue culture in MEFs, after genetic deletion of APC2 induced by Cre-recombinase [35]. Though these cells initiate anaphase, defined cytologically by sister chromatid separation [46], cyclin B remains stable and cells arrest in a pseudo-telophase state with fully separated sister chromatids
These data called into question whether APC/C activity, as well as cyclin B and securin degradation, are essential for sister separation
Summary
Faithful chromosome segregation requires that sister DNA molecules remain attached to one another until anaphase. The association alone of cohesin with DNA is not sufficient for cohesion [3,4,5] and a number of other factors that are thought to license or establish cohesin-based cohesion have been described [6,7,8,9,10,11,12,13,14] These include acetyl-transferases, cohesin binding proteins and, of particular interest, replication fork proteins [14]. Expression of non-cleavable Rad (NC-Rad21), in which the sites normally cleaved by separase are mutated, resulted in delayed sister chromatid resolution in prophase and prometaphase, and a blockage of chromosome arm separation in anaphase, but did not impede centromere separation. Cleavage at the separase-sensitive sites of Rad is important for arm separation, but not for centromere separation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
