Phosphorylation of the chromosomal passenger protein Bir1 is required for localization of Ndc10 to the spindle during anaphase and full spindle elongation
The Saccharomyces cerevisiae inhibitor of apoptosis (IAP) repeat protein Bir1 localizes as a chromosomal passenger. A deletion analysis of Bir1 identified two regions important for function. The C-terminal region is essential for growth, binds Sli15, and is necessary and sufficient for the localization of Bir1 as a chromosomal passenger. The middle region is not essential but is required to localize the inner kinetochore protein Ndc10 to the spindle during anaphase and to the midzone at telophase. In contrast, precise deletion of the highly conserved IAP repeats conferred no phenotype and did not alter the cell cycle delay caused by loss of cohesin. Bir1 is phosphorylated in a cell cycle-dependent manner. Mutation of all nine CDK consensus sites in the middle region of Bir1 significantly decreased the level of phosphorylation and blocked localization of Ndc10 to the spindle at anaphase. Moreover, immunoprecipitation of Ndc10 with Bir1 was dependent on phosphorylation. The loss of Ndc10 from the anaphase spindle prevented elongation of the spindle beyond 7 microm. We conclude that phosphorylation of the middle region of Bir1 is required to bring Ndc10 to the spindle at anaphase, which is required for full spindle elongation.
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[Show abstract] [Hide abstract] ABSTRACT: Studies on budding yeast have exposed the highly conserved mechanisms by which duplicated chromosomes are evenly distributed to daughter cells at the metaphase-anaphase transition. The establishment of proteinaceous bridges between sister chromatids, a function provided by a ring-shaped complex known as cohesin, is central to accurate segregation. It is the destruction of this cohesin that triggers the segregation of chromosomes following their proper attachment to microtubules. Since it is irreversible, this process must be tightly controlled and driven to completion. Furthermore, during meiosis, modifications must be put in place to allow the segregation of maternal and paternal chromosomes in the first division for gamete formation. Here, I review the pioneering work from budding yeast that has led to a molecular understanding of the establishment and destruction of cohesion.
- "Interestingly, distinct CPC subcomplexes exist that appear to carry out specific functions. Among the proteins recruited to the midzone in anaphase by CPC components are the kinetochore protein Ndc10 (Cbf2), which binds to Bir1 (Bouck and Bloom 2005; Widlund et al. 2006; Thomas and Kaplan 2007; Rozelle et al. 2011). Ndc10, Bir1, and Sli15 form an alternative CPC that lacks Ipl1 and regulates spindle elongation (Rozelle et al. 2011). "
[Show abstract] [Hide abstract] ABSTRACT: The propagation of all organisms depends on the accurate and orderly segregation of chromosomes in mitosis and meiosis. Budding yeast has long served as an outstanding model organism to identify the components and underlying mechanisms that regulate chromosome segregation. This review focuses on the kinetochore, the macromolecular protein complex that assembles on centromeric chromatin and maintains persistent load-bearing attachments to the dynamic tips of spindle microtubules. The kinetochore also serves as a regulatory hub for the spindle checkpoint, ensuring that cell cycle progression is coupled to the achievement of proper microtubule-kinetochore attachments. Progress in understanding the composition and overall architecture of the kinetochore, as well as its properties in making and regulating microtubule attachments and the spindle checkpoint, is discussed.
- "The CPC complex is also part of the inner kinetochore, although it is not a core kinetochore complex. Composed of the Ipl1 protein kinase (Aurora B), Sli15 (INCENP), Bir1 (Survivin), and Nbl1 (Borealin) proteins, this complex associates with kinetochores from G1 until anaphase (Widlund et al. 2006; Carmena et al. 2012). The CPC association with the inner kinetochore is mediated via its interaction with CBF3 through Bir1 (Yoon and Carbon 1999; Sandall et al. 2006), and a separate pool may be localized through binding COMA via Sli15 (Knockleby and Vogel 2009). "
[Show abstract] [Hide abstract] ABSTRACT: Cell division in yeast is a highly regulated and well studied event. Various checkpoints are placed throughout the cell cycle to ensure faithful segregation of sister chromatids. Unexpected events, such as DNA damage or oxidative stress, cause the activation of checkpoint(s) and cell cycle arrest. Malfunction of the checkpoints may induce cell death. We previously showed that under oxidative stress, the budding yeast cohesin Mcd1, a homolog of human Rad21, was cleaved by the caspase-like protease Esp1. The cleaved Mcd1 C-terminal fragment was then translocated to mitochondria, causing apoptotic cell death. In the present study, we demonstrated that Bir1 plays an important role in spindle assembly checkpoint and cell death. Similar to H(2)O(2) treatment, deletion of BIR1 using a BIR1-degron strain caused degradation of the securin Pds1, which binds and inactivates Esp1 until metaphase-anaphase transition in a normal cell cycle. BIR1 deletion caused an increase level of ROS and mis-location of Bub1, a major protein for spindle assembly checkpoint. In wild type, Bub1 was located at the kinetochores, but was primarily in the cytoplasm in bir1 deletion strain. When BIR1 was deleted, addition of nocodazole was unable to retain the Bub1 localization on kinetochores, further suggesting that Bir1 is required to activate and maintain the spindle assembly checkpoint. Our study suggests that the BIR1 function in cell cycle regulation works in concert with its anti-apoptosis function.
- "Similar to mammalian survivin (also known as Birc5), the budding yeast Bir1 contains a single RING-finger domain. It is cell cycle regulated and localizes to the centromeres until metaphase-anaphase transition but remains in the equatorial zone as the sister chromatids separate (Uren et al., 1998Uren et al., , 2000 Widlund et al., 2006). Anti-apoptotic function has also been reported for survivin and the yeast homolog Bir1. "