Replication fork block protein, Fob1, acts as an rDNA region specific recombinator in S. cerevisiae

Area of Science:

• Molecular Biology
• Genetics
• Yeast Research

Background:

• Studying homologous recombination in yeast ribosomal DNA (rDNA) offers insights into the stability of repetitive sequences in eukaryotic genomes.
• Previous studies lacked a reliable assay to detect recombination products within the rDNA array, hindering conclusive analysis.

Purpose of the Study:

• To develop and utilize a novel assay for detecting unequal sister-chromatid recombination products in yeast rDNA.
• To investigate the roles of specific genes (FOB1, RAD52, mre11) in rDNA recombination and copy number regulation.

Main Methods:

• Development of a marker-duplication assay to detect unequal sister-chromatid recombination products in yeast rDNA.
• Combined use of the marker-duplication assay with a circular rDNA detection assay.
• Analysis of recombination in wild-type and mutant yeast strains (fob1, rad52, mre11).

Main Results:

• Unequal sister-chromatid recombination occurred throughout the rDNA cluster, primarily between adjacent repeat units.
• Both FOB1 and RAD52 genes were essential for the formation of observed recombinants.
• FOB1 exhibited a gene dosage effect on recombinant levels and rDNA copy number; its role was specific to rDNA, unlike RAD52.
• The mre11 mutation significantly reduced marker-duplication products.

Conclusions:

• FOB1- and RAD52-dependent homologous recombination are fundamental mechanisms driving the gain and loss of rDNA units, thus regulating rDNA copy number.
• FOB1 likely plays a significant role in the regulatory processes governing the copy number of rDNA tandem repeats.