The document discusses mechanisms that promote mono-orientation of sister kinetochores during meiosis I in yeast. It finds that Zip1, a protein involved in synaptonemal complex formation, interacts with components of the Ndc80 kinetochore complex and delays bi-orientation of sister kinetochores when expressed in mitosis. This suggests Zip1 may regulate mono-orientation of sisters similarly to how it arranges chromosomes during synapsis. Deletion of ZIP1 in mutants disrupts this mono-orientation, indicating Zip1 prevents bi-orientation through interacting with functional kinetochores.

1. Zip1 and mono-orientation of sister kinetochores in Meiosis-I

2. Meiosis has two consecutive chromosome segregation events after a single replication phase.

3. In meiosis-I, homologous chromosomes segregate In meiosis-II, sister chromatids segregate

6. Unique meiosis-I feature: Sister kinetochores mono-orient Oocyte kinetochores detected with gold-labeled anti-CENPE (From Lee J. et al. Molec Reprod Dev 56: 51-62, 2000)

7. Monopolin promotes sister- kinetochores’ mono-orientation (Petronczki M et al. Cell 112:423-440, 2003)

9. Physical Interaction between Meiosis Specific Proteins and Outer Kinetochore Components Recombination/repair Spore wall formation RNA metabolism Kinase Other 1. Data source: Saccharomyces Genome Database. 2. Number of lines denotes the number of kinetochore proteins a meiotic protein interacts with. MIND NDC80 COMA DAM1 MCK1 RAD50 SSP1 MND2 CSM1 MMS22 MPS3 SLX5 BUB3 PHO91 ATG1 PKH2 HMT1 PGD1 SPO21 ADY3 MPC54 SPO71 MRE11 DMC1 MUM2 MDS3 ZI P1 REC107 MAD1

10. Zip1 Interacts with Two Different Proteins, Nuf2 and Spc24, of the Ndc80 Kinetochore Complex!

11. Synaptonemal Complex & Zip1 Page & Hawley (2004) Ann. Rev. Cell and Developmental Biology http://8e.devbio.com/printer.php?ch=2&id=188 Mouse SCs LE Red1 , Hop1 CE/TF Zi p1 Yeast SC proteins

13. The Ndc80 Kinetochore Complex Architecture and flexibility of the yeast Ndc80 kinetochore complex. Wang HW, Long S, Ciferri C, Westermann S, Drubin D, Barnes G, Nogales E. J Mol Biol. 2008, 383: 894-903.

14. Does Zip1 Link Sister Kinetochores in a Manner Analogous to its Arrangement in SC? Bardhan A. Journal of Biosciences 2010, 35: 485-495

15. Zip1 regulates mono-orientation of sister kinetochores?

16. DAPI GFP spindle CEN Overlay Mono-orient Bi-orient Kinetics of first meiosis Segregation of sister CEN s in meiosis-I Kinetochore orientation in metaphase I N = 300 P= 0.0105 N = 70-80 P= 0.014

17. Zip1 expressed in mitosis delays bi-orientation of sister kinetochores 1. Zip1 expressed from galactose inducible promoter 2. Biorientation experiment after King et al 2007 PLoS One 2 e342 Glucose: Zip1 OFF Galactose: Zip1 ON mad2  mad2  / Zip1 mad3  mad3  / Zip1 sgo1  bub1  K bub1  K/ Zip1 sgo1  / Zip1

19. Deletion of ZIP1 in mam1 ∆ ipl1 mn ‘randomizes’ sister CEN segregation Initial attachment ~70% ~50% ~50% mam1  mam1  zip1  ~30%

20. Two pathways Monopolin complex Promote mono-orientation (Fusion of sister kinetochores To generate a single functional one? Toth et al. 2000) Zip1 Prevent Bi-orientation (Works on two functional kinetochores)

21. Acknowledgement The experiments were designed and executed by Amit Bardhan, in the lab of Dean Dawson at Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation.