Sap1, a protein that binds to sequences required for mating-type switching, is essential for viability in Schizosaccharomyces pombe.
The pattern of mating-type switching in cell pedigrees of the fission yeast Schizosaccharomyces pombe is dictated by the inheritance of specific DNA chains at the mating-type locus (mat1). The recombination event essential for switching is initiated by a site-specific double-strand break at mat1. The switch-activating protein, Sap1, binds in vitro to a mat1 cis-acting site that was shown earlier to be essential for efficient mating-type switching. We isolated the sap1 gene by using oligonucleotides corresponding to the amino acid sequence of purified Sap1 protein. The sequence of that gene predicted a 30-kDa protein with no significant homology to other canonical DNA-binding protein motifs. To facilitate its biochemical characterization, Sap1 was expressed in Escherichia coli. The protein expressed in bacteria displayed the same DNA-binding specificities as the protein purified from S. pombe. Interestingly, analysis of a sap1 null mutation showed that the gene is essential for growth even in a strain in which mating-type switching is prohibited because of a defect in generation of the double-strand break. Thus, the sap1 gene product implicated in mating-type switching is shown to be essential for cell viability.
Arcangioli
B
B
Laboratory of Eukaryotic Gene Expression, NCI-Frederick Cancer Research and Development Center, Maryland 21702-1201.
Copeland
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TD
Klar
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AJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000302:isolation & purification; D005656:Fungal Proteins / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000254:growth & development*; D029702:Schizosaccharomyces pombe Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; C085981:Sap1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins