Behavior of dicentric chromosomes in budding yeast

Area of Science:

• Genetics
• Molecular Biology
• Cell Biology

Background:

• DNA double-strand breaks (DSBs) are critical DNA lesions.
• Dicentric chromosomes, with two centromeres, lead to DSBs during mitosis.
• Repair of these DSBs contributes to genomic instability and phenotypic diversity.

Purpose of the Study:

• To investigate if the spatial position of DSBs influences their repair mechanisms.
• To analyze how the distance between centromeres in dicentric chromosomes affects DSB repair outcomes.
• To identify genetic factors governing DSB repair pathway selection.

Main Methods:

• Analysis of monocentric derivative chromosomes from cells with varying dicentric chromosome lengths.
• Classification of repair products into homology-based (homologous recombination, single-strand annealing) and end-joining (non-homologous, micro-homology mediated) pathways.
• Assessment of genetic dependencies on key repair proteins (Rad52, Lif1, Mrc1).

Main Results:

• Two major repair product classes, homology-based and end-joining, were identified.
• The distribution of these repair products varied significantly with the distance between the two centromeres.
• Distinct repair pathway choices were observed for DSBs located in pericentromeric chromatin versus chromosome arms.

Conclusions:

• DSB repair is spatially regulated within chromosomes.
• The distance between centromeres dictates the choice between homology-based and end-joining repair pathways.
• Genetic factors like Rad52, Lif1, and Mrc1 play crucial roles in differential DSB repair pathway selection.