A Functional Link Between Bir1 and the Saccharomyces cerevisiae Ctf19 Kinetochore Complex Revealed Through Quantitative Fitness Analysis

• Main Authors: Vasso Makrantoni, Adam Ciesiolka, Conor Lawless, Josefin Fernius, Adele Marston, David Lydall, Michael J. R. Stark
• Format: Article
• Language: English
• Published: Oxford University Press 2017-09-01
• Series: G3: Genes, Genomes, Genetics
• Subjects: Bir1; Chromosome biorientation; Kinetochore; Iml3-Chl4 complex; yeast
• Online Access: http://g3journal.org/lookup/doi/10.1534/g3.117.300089

The chromosomal passenger complex (CPC) is a key regulator of eukaryotic cell division, consisting of the protein kinase Aurora B/Ipl1 in association with its activator (INCENP/Sli15) and two additional proteins (Survivin/Bir1 and Borealin/Nbl1). Here, we report a genome-wide genetic interaction screen in Saccharomyces cerevisiae using the bir1-17 mutant, identifying through quantitative fitness analysis deletion mutations that act as enhancers and suppressors. Gene knockouts affecting the Ctf19 kinetochore complex were identified as the strongest enhancers of bir1-17, while mutations affecting the large ribosomal subunit or the mRNA nonsense-mediated decay pathway caused strong phenotypic suppression. Thus, cells lacking a functional Ctf19 complex become highly dependent on Bir1 function and vice versa. The negative genetic interaction profiles of bir1-17 and the cohesin mutant mcd1-1 showed considerable overlap, underlining the strong functional connection between sister chromatid cohesion and chromosome biorientation. Loss of some Ctf19 components, such as Iml3 or Chl4, impacted differentially on bir1-17 compared with mutations affecting other CPC components: despite the synthetic lethality shown by either iml3∆ or chl4∆ in combination with bir1-17, neither gene knockout showed any genetic interaction with either ipl1-321 or sli15-3. Our data therefore imply a specific functional connection between the Ctf19 complex and Bir1 that is not shared with Ipl1.