Spo13 maintains centromeric cohesion and kinetochore coorientation during meiosis I.
BACKGROUND
The meiotic cell cycle, the cell division cycle that leads to the generation of gametes, is unique in that a single DNA replication phase is followed by two chromosome segregation phases. During meiosis I, homologous chromosomes are segregated, and during meiosis II, as in mitosis, sister chromatids are partitioned. For homolog segregation to occur during meiosis I, physical linkages called chiasmata need to form between homologs, sister chromatid cohesion has to be lost in a stepwise manner, and sister kinetochores must attach to microtubules emanating from the same spindle pole (coorientation).


RESULTS
Here we show that the meiosis-specific factor Spo13 functions in two key aspects of meiotic chromosome segregation. In cells lacking SPO13, cohesin, which is the protein complex that holds sister chromatids together, is not protected from removal around kinetochores during meiosis I but is instead lost along the entire length of the chromosomes. We furthermore find that Spo13 promotes sister kinetochore coorientation by maintaining the monopolin complex at kinetochores. In the absence of SPO13, Mam1 and Lrs4 disassociate from kinetochores prematurely during pro-metaphase I and metaphase I, resulting in a partial defect in sister kinetochore coorientation in spo13 Delta cells.


CONCLUSIONS
Our results indicate that Spo13 has the ability to regulate both the stepwise loss of sister chromatid cohesion and kinetochore coorientation, two essential features of meiotic chromosome segregation.
Lee
Brian H
BH
Center for Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
Kiburz
Brendan M
BM
Amon
Angelika
A
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D002503:Centromere / Q000378:metabolism*; D020090:Chromosome Segregation / Q000502:physiology*; D020732:Cytogenetic Analysis; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins; D047468:Immunoprecipitation; D018386:Kinetochores / Q000378:metabolism*; D008540:Meiosis / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D018797:Cell Cycle Proteins; C474336:LRS4 protein, S cerevisiae; D009687:Nuclear Proteins; C097192:SPO13 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C107004:mam1 protein, S pombe; D049452:Green Fluorescent Proteins