sic1 mutation leads to rDNA instability by partial duplication with SIR4.

Area of Science:

• Genetics
• Molecular Biology
• Yeast Genetics

Background:

• The ribosomal RNA gene cluster (rDNA) in Saccharomyces cerevisiae is a fragile genomic region.
• Recombination within the rDNA array can lead to copy number changes, impacting cellular function.
• The relationship between rDNA stability and the stability of other genomic loci is not well understood.

Purpose of the Study:

• To investigate the mechanisms underlying genomic instability in yeast.
• To explore the connection between ribosomal RNA gene cluster (rDNA) stability and the stability of other genomic regions.
• To identify genetic factors that influence both rDNA and chromosome stability.

Main Methods:

• Isolation and characterization of a yeast mutant exhibiting instability in both rDNA and chromosome IV.
• Analysis of Ty element-mediated recombination events.
• Quantification of SIR4 gene dosage in the identified mutant.

Main Results:

• A novel yeast mutant, sic1, displayed instability in both rDNA and chromosome IV (chr.IV).
• Ty element-mediated ectopic recombination was identified as the cause of chr.IV partial duplication and elongation.
• Increased SIR4 gene dosage, resulting from chr.IV duplication, was found to induce rDNA instability.

Conclusions:

• Genomic instability in Saccharomyces cerevisiae can affect multiple genomic regions simultaneously.
• Ty element activity plays a significant role in mediating large-scale genomic rearrangements.
• A link exists between the stability of the ribosomal RNA gene cluster (rDNA) and other chromosomal regions, mediated by gene dosage effects.