Cloning, expression, and complementation test of the RNA lariat debranching enzyme cDNA from mouse

The RNA lariat debranching enzyme of mouse (mDBR1) was cloned by screening a NIH/3T3 cDNA library. The sequence of full-length mDBR1 cDNA contained a single 515 amino acid open reading frame of 58 kDa protein, Comparison of t he amino acid sequence of mDBR1 to other DBR proteins showed 40%, 44%, 43%, 42%, and 80% identity to Saccharomyces cerevisiae, Schizosaccharomyces pom be, Caenorhabditis elegans, Drosophila melanogaster, and human debranching enzymes, respectively, The mDBR1 cDNA was shown to be functional in an inte rspecies specific complementation experiment, and an in vitro debranching e nzyme assay. Mouse DBR1 could complement the intron accumulation phenotype of a S, cerevisiae dbr1 null mutant strain. However, the level of complemen tation depended on the copy number of the mDBR1 cDNA, The integration of th e mDBR1 cDNA in the chromosome of S, pombe also complemented both intron ac cumulation and slow growth phenotypes of the S, pombe dbr1 knock-out mutant strain.