Behavior of dicentric chromosomes in budding yeast.

Diana Cook,Colleen Lawrimore,Kerry Bloom,Sarah Grant,Patrick Cusick,Elaine Yeh,Sarah Long,John Stanton,Beth A Sullivan

doi:10.1371/journal.pgen.1009442

Diana Cook, Colleen Lawrimore + Show 7 more

Open Access

https://doi.org/10.1371/journal.pgen.1009442

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Journal: PLoS Genetics	Publication Date: Mar 18, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: University of North Carolina at Chapel Hill

Abstract

DNA double-strand breaks arise in vivo when a dicentric chromosome (two centromeres on one chromosome) goes through mitosis with the two centromeres attached to opposite spindle pole bodies. Repair of the DSBs generates phenotypic diversity due to the range of monocentric derivative chromosomes that arise. To explore whether DSBs may be differentially repaired as a function of their spatial position in the chromosome, we have examined the structure of monocentric derivative chromosomes from cells containing a suite of dicentric chromosomes in which the distance between the two centromeres ranges from 6.5 kb to 57.7 kb. Two major classes of repair products, homology-based (homologous recombination (HR) and single-strand annealing (SSA)) and end-joining (non-homologous (NHEJ) and micro-homology mediated (MMEJ)) were identified. The distribution of repair products varies as a function of distance between the two centromeres. Genetic dependencies on double strand break repair (Rad52), DNA ligase (Lif1), and S phase checkpoint (Mrc1) are indicative of distinct repair pathway choices for DNA breaks in the pericentromeric chromatin versus the arms.

Highlights

Chromosomes containing two functional centromeres are subject to a breakagefusion-bridge (BFB) cycle as cells divide [1,2,3,4]
We have found that chromosome breaks between two centromeres that both lie within the pericentromeric region of the chromosomes are repaired via pathways that do not rely on sequence homology (MMEJ or NHEJ)
Chromosome breaks in dicentric chromosomes whose centromeres are separated by > 20 kb are repaired via pathways that rely mainly on sequence homology (HR, single-strand annealing (SSA))

Summary

Introduction

Chromosomes containing two functional centromeres (dicentrics) are subject to a breakagefusion-bridge (BFB) cycle as cells divide [1,2,3,4]. Using a conditionally functional centromere (transcriptional promoter GAL1 adjacent to eCEN3, GALCEN3), we can regulate onset of the BFB cycle in order to examine breakage and subsequent DNA repair pathways [5,6]. In cells with a dicentric chromosome, there is an approximately 50/50 chance that centromeres on the same DNA strand will go to the same or opposite spindle pole during mitosis [7]. When centromeres on the same chromatid strand go to the same pole, sister chromatids segregate without DNA breakage. Chromosome breakage, and the resulting BFB cycle, ensues when centromeres on the same strand orient to opposite poles [7]. About 50% of the DNA breaks occur within 10 kb of either of the two centromeres [10,11]

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