Isolation of the gene encoding yeast single-stranded nucleic acid binding protein 1

Area of Science:

• Molecular Biology
• Yeast Genetics

Background:

• Single-stranded nucleic acid binding proteins play crucial roles in DNA replication, repair, and recombination.
• The SSB-1 protein in yeast is a key player in maintaining genomic stability.

Purpose of the Study:

• To isolate and characterize the yeast SSB-1 gene.
• To determine the essentiality of the SSB-1 gene for yeast viability.
• To investigate the presence of related genes and proteins in yeast.

Main Methods:

• Screening of a lambda gt11 genomic DNA library.
• Gene cloning and manipulation using yeast vectors (YEp24).
• Gene disruption and analysis of resulting yeast strains.
• Protein expression in Escherichia coli using a phage T7 system.
• Southern analysis and protein blotting (immunoblotting).

Main Results:

• The yeast SSB-1 gene was isolated and mapped to a specific DNA fragment.
• Overexpression of SSB-1 in yeast led to a 3-fold increase in protein and a 10-fold increase in mRNA.
• Disruption of the SSB-1 gene did not affect yeast spore germination or growth, indicating it is non-essential.
• No SSB-1 or related active proteins were detected in disrupted gene strains.
• Evidence suggests the existence of a second, related SSB gene and two immunologically similar proteins (55 kDa and 75 kDa).

Conclusions:

• The yeast SSB-1 gene is non-essential for cell viability, suggesting functional redundancy.
• The study provides evidence for additional related genes and proteins within the yeast genome that may compensate for SSB-1 loss.