sister-chromatid cohesion is essential for proper chromosome segregation and faithful transmission
of the genome during the cell cycle (morales and losada， 2018; uhlmann， 2016) failure to estab-
lish or resolve cohesion in a timely manner leads to genomic instability and aneuploidy sister-chro-
matid cohesion is mediated by cohesin， a ring-shaped atpase machine that consists of smc1a，
smc3， rad21， and either stag1 or stag2 in human somatic cells (haarhuis et al， 2014;
losada and hirano， 2005; nasmyth and haering， 2009; onn et al， 2008; peters et al， 2008;
zheng and yu， 2015) cohesin rings topologically entrap dna to generate physical linkages
between sister chromatids and enable cohesion cohesin regulates other chromosome-based pro-
cesses， such as dna repair， transcription， and chromosome folding (merkenschlager and odom，
2013; wu and yu， 2012) these other functions of cohesin likely also involve the topological entrap-
ment of chromosomes or possibly the extrusion of dna loops (barrington et al， 2017;
davidson et al， 2016; haarhuis et al， 2017)
cohesin is loaded onto chromosomes in telophase and g1 by the s2/4 plex (nipbl/mau2
in humans)(ciosk et al， 2000; gillespie and hirano， 2004; takahashi et al， 2004; tonkin et al，
2004; watrin et al， 2006) before dna replication， the chromosome-bound cohesin is dynamic and
is actively removed from chromosomes by the cohesin-releasing factor wapl with the help of thescaffolding protein pds5a or pds5b (chan et al， 2012; kueng et al， 2006; lopez-serra et al，
2013; ouyang and yu， 2017; ouyang et al， 2013; ouyang et al， 2016) during dna replication
in s phase， a pool of cohesin is converted to the cohesive form， which stably associates with chromo-
somes and mediates sister-chromatid cohesion (gerlich et al， 2006; kueng et al， 2006) in human
cells， cohesion establishment requires the acetylation