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mei-3, a recombination and repair gene of Neurospora crassa, encodes a RecA-like protein
R Cheng1, T I Baker, C E Cords
1Department of Microbiology, University of New Mexico School of Medicine, Albuquerque 87131-5276.
Abstract:
Neurospora crassa mei-3 is a mutant which exhibits meiotic and mitotic defects and mutagen sensitivity. Its defect is believed to be in recombination and repair. We have cloned the mei-3 gene from a N. crassa cosmid library of genomic DNA. Restriction fragment length polymorphism analysis determined the location of the cloned fragment was on chromosome one in approximately the same position that was previously reported for mei-3 by classical genetic methods. Deletion analysis showed the approximate coding region of mei-3 on the cloned genomic fragment. Northern blot analysis identified a 900-bp transcript. Sequencing revealed a 798-bp open reading frame with high coding preference which could encode a protein having a molecular weight of approximately 29,000. The predicted protein product of mei-3 has significant identity to the Rad51 and Dmc1 proteins from Saccharomyces cerevisiae. The mei-3 gene and both yeast genes have significant primary sequence homology with RecA, a recombination protein identified in Escherichia coli. The results suggest RecA-like proteins involved in DNA recombination and repair are highly conserved in eukaryotes.
Insights
The Neurospora crassa mei-3 gene, crucial for DNA repair and recombination, was cloned and sequenced. Its protein product is similar to conserved RecA-like proteins in yeast and E. coli.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The mei-3 mutant in Neurospora crassa displays defects in meiosis, mitosis, and heightened sensitivity to mutagens.
- These defects are hypothesized to stem from issues in DNA recombination and repair pathways.
Purpose of the Study:
- To clone and characterize the mei-3 gene from Neurospora crassa.
- To elucidate the function of the mei-3 gene product in DNA recombination and repair.
Main Methods:
- Gene cloning using a Neurospora crassa cosmid library.
- Restriction fragment length polymorphism and deletion analyses for gene mapping.
- Northern blot analysis to determine transcript size.
- DNA sequencing to identify the open reading frame and predict protein characteristics.
Main Results:
- The mei-3 gene was successfully cloned and mapped to chromosome one.
- A 900-bp transcript and a 798-bp open reading frame were identified.
- The predicted mei-3 protein (approx. 29 kDa) shows significant homology to Rad51 and Dmc1 from Saccharomyces cerevisiae and RecA from Escherichia coli.
Conclusions:
- The mei-3 gene encodes a RecA-like protein involved in DNA recombination and repair.
- These findings highlight the high conservation of RecA-like proteins across eukaryotes, underscoring their fundamental role in genome stability.