LAB-1 Targets PP1 and Restricts Aurora B Kinase upon Entrance into Meiosis to Promote Sister Chromatid Cohesion

Successful execution of the meiotic program depends on the timely establishment and removal of sister chromatid cohesion. lab-1 has been proposed to act in the latter by preventing the premature removal of the meiosis-specific cohesin rec-8 at metaphase i in c. elegans,yet the mechanism and scope of lab-1 function remained unknown. here we identify an unexpected earlier role for lab-1 in promoting the establishment of sister chromatid cohesion in prophase i. lab-1 and rec-8 are both required for the chromosomal association of the cohesin complex subunit smc-3. depletion of lab-1 results in partial loss of sister chromatid cohesion in rec-8 and coh-4 coh-3 mutants and further enhanced chromatid dissociation in worms where all three kleisins are mutated. moreover,lab-1 depletion results in increased aurora b kinase (air-2) signals in early prophase i nuclei,coupled with a parallel decrease in signals for the pp1 homolog,gsp-2. finally,lab-1 directly interacts with gsp-1 and gsp-2. we propose that lab-1 targets the pp1 homologs to the chromatin at the onset of meiosis i,thereby antagonizing air-2 and cooperating with the cohesin complex to promote sister chromatid association and normal progression of the meiotic program. © 2012 tzur et al.