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Characterization of the mouse Rep-3 gene: sequence similarities to bacterial and yeast mismatch-repair proteins
K Liu1, L Niu, J P Linton
1Department of Biology, Emory University, Atlanta, GA 30322.
Abstract:
The mouse Rep-3 gene is transcribed divergently from the same promoter region as the dihydrofolate reductase-encoding gene and has a deduced amino-acid sequence that shares identity with the bacterial protein, MutS, which is involved in DNA mismatch repair. We have cloned Rep-3, mapped it and sequenced all of the known exons and their intron junction sequences. We find that the open reading frame is considerably larger than initially reported and that the most abundant form of Rep-3 mRNA encodes a protein of 123 kDa. The gene spans at least 134 kb and consists of 26 exons, including several alternatively spliced exons. All of the exon/intron junctions match the expected consensus sequences with the exception of the splice junctions for intron 6, which has AT and AC dinucleotides instead of the usual GT and AG bordering the exon sequences. The junction sequences for this intron share consensus sequences with three intron sequences from other genes, thereby helping to establish an alternative consensus sequence.
Insights
The mouse Rep-3 gene, involved in DNA repair, has a larger open reading frame than previously known, encoding a 123 kDa protein. Its gene structure includes alternative splicing and unusual intron splice junctions.
Area of Science:
- Genetics and Molecular Biology
- DNA Repair Mechanisms
Background:
- The mouse Rep-3 gene shares promoter regions with the dihydrofolate reductase gene.
- Rep-3's deduced amino acid sequence shows homology to bacterial MutS, a protein critical for DNA mismatch repair.
Purpose of the Study:
- To clone, map, and sequence the mouse Rep-3 gene, including its exons and intron-exon junctions.
- To characterize the full-length Rep-3 protein and its mRNA transcript.
Main Methods:
- Gene cloning and mapping techniques.
- DNA sequencing of exons and intron-exon boundaries.
- Analysis of mRNA transcripts to determine protein size.
Main Results:
- The Rep-3 gene spans at least 134 kb and comprises 26 exons, with evidence of alternative splicing.
- The most abundant Rep-3 mRNA encodes a 123 kDa protein, indicating a larger open reading frame than previously reported.
- Intron 6 splice junctions exhibit non-canonical AT/AC dinucleotides, sharing consensus with other gene introns, suggesting an alternative consensus sequence.
Conclusions:
- The mouse Rep-3 gene is extensively structured, featuring alternative splicing and unique splice site variations.
- The characterized 123 kDa protein product suggests a more complex role for Rep-3 in DNA repair pathways.