Spindle disruption or DNA damage prevents sister chromatid separation through the activation of checkpoint pathways that inhibit anaphase entry by stabilizing the anaphase inhibitor Pds1. Mutation of CDC55, which encodes a B regulatory subunit of protein phosphatase 2A (PP2A), results in precocious sister chromatid separation when spindle is disrupted. Here we report that decreased Pds1 levels ...

In Drosophila males and females mutant for the ord gene, sister chromatids prematurely disjoin in meiosis. We have isolated five new alleles of ord and analyzed them both as homozygotes and in trans to deficiencies for the locus, and we show that ord function is necessary early in meiosis of both sexes. Strong ord alleles result in chromosome nondisjunction in meiosis I that appears to be the c...

Background: The maternal age effect for trisomy is well known. However what is less established is whether certain women are more (or less) prone to segregation errors, independent of age. Trisomy arises primarily through maternal meiosis I chromosome segregation errors however the precise mechanism by which these errors occur is unclear. Current dogma attributes the origin of trisomy to malseg...

INTRODUCTION Aneuploidy (the presence of extra or missing chromosomes) arises primarily through chromosome segregation errors in the oocyte at meiosis I but the details of mechanism by which such errors occur in humans are the subject of some debate. It is generally believed that aneuploidy arises primarily as a result of segregation of a whole chromosome to the same pole as its homologue (non-...

It is well documented that inactivation of essential cohesion proteins results in precocious sister-chromatid separation. On average, however, only approximately 55% of cohesin-deficient budding yeast cells arrested prior to anaphase contain separated sister chromatids , suggesting that cohesin-independent factors also contribute to sister-chromatid pairing. Recently, redundant pairing mechanis...

We have developed a system that utilizes human DNA-derived yeast artificial chromosomes (YACs) as marker chromosomes to study factors that contribute to the fidelity of meiotic chromosome transmission. Since aneuploidy for the YACs does not affect spore viability, different classes of meiotic missegregation can be scored accurately in four-viable-spore tetrads including precocious sister separa...

Sister chromatid separation depends on the release of cohesion by the activity of Esp1, a member of the caspase family [1, 2]. In budding yeast, Esp1p is kept inactive by its association with Pds1p, until the onset of anaphase, when Pds1p is ubiquitinated by the APC/Cdc20 complex [3--5] and subsequently degraded by the 26S proteasome. Pds1 is not an essential gene in budding yeast, but is requi...

BACKGROUND Follicular fluid meiosis-activating sterol (FF-MAS) protects young oocytes from precocious chromatid separation (predivision). Reduced expression of cohesion and checkpoint proteins and predivision has been hypothesized to occur in age-related aneuploidy in oocytes. METHODS To know whether FF-MAS also protects aged oocytes from predivision and from age-related non-disjunction, we a...

The cohesin complex topologically encircles chromosomes and mediates sister chromatid cohesion to ensure accurate chromosome segregation upon cell division. Cohesin also participates in DNA repair and gene transcription. The Nipped-B-Mau2 protein complex loads cohesin onto chromosomes and the Pds5-Wapl complex removes cohesin. Pds5 is also essential for sister chromatid cohesion, indicating tha...

Meiotic cohesin serves in sister chromatid linkage and DNA repair until its subunit Rec8 is cleaved by separase. Separase is activated when its inhibitor, securin, is polyubiquitinated by the Cdc20 regulated anaphase-promoting complex (APC(Cdc20)) and consequently degraded. Differently regulated APCs (APC(Cdh1), APC(Ama1)) have not been implicated in securin degradation at meiosis I. We show th...