The aurora B kinase AIR-2 regulates kinetochores during mitosis and is required for separation of homologous Chromosomes during meiosis.
BACKGROUND
Mitotic chromosome segregation depends on bi-orientation and capture of sister kinetochores by microtubules emanating from opposite spindle poles and the near synchronous loss of sister chromatid cohesion. During meiosis I, in contrast, sister kinetochores orient to the same pole, and homologous kinetochores are captured by microtubules emanating from opposite spindle poles. Additionally, mechanisms exist that prevent complete loss of cohesion during meiosis I. These features ensure that homologs separate during meiosis I and sister chromatids remain together until meiosis II. The mechanisms responsible for orienting kinetochores in mitosis and for causing asynchronous loss of cohesion during meiosis are not well understood.


RESULTS
During mitosis in C. elegans, aurora B kinase, AIR-2, is not required for sister chromatid separation, but it is required for chromosome segregation. Condensin recruitment during metaphase requires AIR-2; however, condensin functions during prometaphase, independent of AIR-2. During metaphase, AIR-2 promotes chromosome congression to the metaphase plate, perhaps by inhibiting attachment of chromatids to both spindle poles. During meiosis in AIR-2-depleted oocytes, congression of bivalents appears normal, but segregation fails. Localization of AIR-2 on meiotic bivalents suggests this kinase promotes separation of homologs by promoting the loss of cohesion distal to the single chiasma. Inactivation of the phosphatase that antagonizes AIR-2 causes premature separation of chromatids during meiosis I, in a separase-dependent reaction.


CONCLUSIONS
Aurora B functions to resolve chiasmata during meiosis I and to regulate kinetochore function during mitosis. Condensin mediates chromosome condensation during prophase, and condensin-independent pathways contribute to chromosome condensation during metaphase.
Kaitna
Susanne
S
Research Institute of Molecular Pathology (IMP), Dr. Bohr-Gasse 7, A-1030, Vienna, Austria.
Pasierbek
Pawel
P
Jantsch
Michael
M
Loidl
Josef
J
Glotzer
Michael
M
D000251:Adenosine Triphosphatases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000818:Animals; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D002842:Chromatids / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D020090:Chromosome Segregation; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D000939:Epitopes; D015801:Helminth Proteins / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D018386:Kinetochores / Q000201:enzymology*; D008540:Meiosis; D008677:Metaphase; D008938:Mitosis; D008954:Models, Biological; D046912:Multiprotein Complexes; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D000939:Epitopes; D015801:Helminth Proteins; D006657:Histones; D046912:Multiprotein Complexes; D010750:Phosphoproteins; C118999:bir-1 protein, C elegans; C108312:condensin complexes; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; C491506:air-2 protein, C elegans; D000251:Adenosine Triphosphatases