When Mps1 was inactive, the majority of centromeres showed mono-orientation on the bipolar spindle, and in addition, the spindle became longer than normal and was sometimes discontinuous in the middle [8].
What causes mono-orientation of sister centromeres when Mps1 is inactive?
Our results therefore suggest that Bub3 is involved in converting the mono-orientation of chromosomes to bi-orientation.
We show that fission yeast Ark1 is required for the faithful mono-orientation of sister chromatids in meiosis-I.
The mono-orientation of CEN3 signals in mps1-as1 was not due to failure of DNA replication.
The depletion of Moa1 together with Rec12 or of Rec8 entirely disrupts the mono-orientation of sister chromatids at meiosis-I.
This is consistent with the observation that fission yeast has an additional system ensuring mono-orientation of sister kinetochores during meiosis I [22].
After release from cdc34-2 andest additiontiof of 1NM-PP1, mps1-as1 cellshowedextensiveive mono-orientation of both pairs of sister CEN5s and CEN15s, as expected.
Unexpectedly, Ark1 is also necessary for the faithful mono-orientation of sister chromatids in meiosis-I, even though the canonical mono-orientation pathway, which depends on Moa1 and Rec8, seems intact.
Furthermore, the localization of Rec8 at the centromeric central core, which is important for mono-orientation of kinetochores (Watanabe et al, 2001; Yokobayashi et al, 2003), was intact in the ark1 s.o. cells (Supplementary Figure S8).
Similarly, mitosis-like chromosomes can be generated by deleting rec12+, which is required for recombination, and moa1+, the gene product of which is required for the mono-orientation of sister kinetochores in concert with Rec8 (Yokobayashi and Watanabe, 2005).
