Temperature-sensitive mutations in the yeast DNA polymerase I gene

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• DNA polymerase I is essential for DNA replication and repair in Saccharomyces cerevisiae.
• Temperature-sensitive mutations provide a tool to study essential genes under controlled conditions.
• Understanding POL1 function is crucial for comprehending genome stability.

Purpose of the Study:

• To isolate and characterize temperature-sensitive mutations in the POL1 gene.
• To develop a general method for identifying temperature-sensitive and null mutations.
• To investigate the in vivo effects of POL1 mutations on DNA synthesis and cell morphology.

Main Methods:

• Isolation of temperature-sensitive mutations in POL1 using a plasmid shuffling system.
• Characterization of DNA polymerase I activity in vitro at different temperatures.
• Assessment of DNA and RNA synthesis in vivo in mutant strains.
• Microscopic analysis of cell morphology in temperature-sensitive mutants.

Main Results:

• Seven thermolabile POL1 mutations were identified, conferring temperature sensitivity for growth.
• Mutant DNA polymerase I enzymes showed defects at both permissive and restrictive temperatures.
• In vivo DNA synthesis was impaired in all mutants at the restrictive temperature.
• Mutants exhibited characteristic dumbbell-shaped cell morphology with nuclear migration defects.

Conclusions:

• The POL1 gene is essential for DNA synthesis and cell cycle progression in Saccharomyces cerevisiae.
• The identified mutations provide valuable tools for studying DNA polymerase I function.
• The developed method is effective for isolating temperature-sensitive mutations in essential genes.