BioProject

Accurate chromosome segregation requires that sister kinetochores biorient and attach to microtubules from opposite poles. More...

Accurate chromosome segregation requires that sister kinetochores biorient and attach to microtubules from opposite poles. Kinetochore biorientation relies on the underlying centromeric chromatin, which provides a platform to assemble the kinetochore and to recruit the regulatory factors that ensure the high fidelity of this process. To identify the centromeric chromatin determinants that contribute to chromosome segregation, we performed two complementary unbiased genetic screens using a library of mutants in every residue of histone H3 and H4. In one screen, we identified mutants that lead to increased loss of a non-essential chromosome. In the second screen, we isolated mutants whose viability depends on a key regulator of biorientation, the Aurora B protein kinase. Nine mutations, H3 Q5A, H3 R40A, H3 G44A, H3 R53A, H3 N108A, H3 L109A, H4 K44A, H4 V81A, and H4 Y98A, were common to both screens and exhibited kinetochore biorientation defects. Five of the mutants map near the unstructured nucleosome entry site and their genetic interaction with decreased Ipl1 function can be suppressed by increasing the dosage of the Sgo1 protein. In addition, the composition of purified kinetochores was altered in five of the mutants. Together, this work identifies previously unknown histone residues involved in chromosome segregation and lays the foundation for future studies of the role of the underlying chromatin structure in segregation. Overall design: Two channel microarrays were used. RNA isolated from a large amount of wt yeast from a single culture was used as a common reference. Two independent cultures were hybridized on two separate microarrays. For the first hybridization the Cy5 (red) labeled cRNA from the deletion mutant is hybridized together with the Cy3 (green) labeled cRNA from the common reference. For the replicate hybridization, the labels are swapped. Each gene is represented twice on the microarray, resulting in four measurements per mutant. Wt cultures were grown parallel to the deletion mutants to assess day-to-day variance. Less...