This presumed domain is found at the C terminus of lariat debranching enzyme. This domain is always found in association with a metallo-phosphoesterase domain IPR004843 . RNA lariat debranching enzyme is capable of digesting a variety of branched nucleic acid substrates and multicopy single-stranded DNAs. The enzyme degrades intron lariat structures during splicing.
Severe growth defect in a Schizosaccharomyces pombe mutant defective in intronlariat degradation.
Mol Cell Biol. 1997; 17: 809-18
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The cDNAs and genes encoding the intron lariat-debranching enzyme were isolatedfrom the nematode Caenorhabditis elegans and the fission yeastSchizosaccharomyces pombe based on their homology with the Saccharomycescerevisiae gene. The cDNAs were shown to be functional in an interspecificcomplementation experiment; they can complement an S. cerevisiae dbr1 nullmutant. About 2.5% of budding yeast S. cerevisiae genes have introns, and theaccumulation of excised introns in a dbr1 null mutant has little effect on cellgrowth. In contrast, many S. pombe genes contain introns, and often multipleintrons per gene, so that S. pombe is estimated to contain approximately 40 timesas many introns as S. cerevisiae. The S. pombe dbr1 gene was disrupted and shown to be nonessential. Like the S. cerevisiae mutant, the S. pombe null mutantaccumulated introns to high levels, indicating that intron lariat debranchingrepresents a rate-limiting step in intron degradation in both species. Unlike theS. cerevisiae mutant, the S. pombe dbr1::leu1+ mutant had a severe growth defect and exhibited an aberrant elongated cell shape in addition to an intronaccumulation phenotype. The growth defect of the S. pombe dbr1::leu1+ strainsuggests that debranching activity is critical for efficient intron RNAdegradation and that blocking this pathway interferes with cell growth.
Isolation and characterization of the gene encoding yeast debranching enzyme.
Cell. 1991; 65: 483-92
Display abstract
Using a genetic screen aimed at identifying cellular factors involved in Ty1transposition, we have identified a mutation in a host gene that reduces Ty1transposition frequency. The mutant, dbr1, is also defective in the process ofintron turnover. In dbr1 cells, excised introns derived from a variety ofpre-mRNAs are remarkably stable and accumulate to levels exceeding that of thecorresponding mRNA. The stable excised introns accumulate in the form of a lariatthat is missing the linear sequences 3' of the branchpoint. The DBR1 gene hasbeen isolated by complementation of the transposition phenotype. DBR1 is shown toencode debranching enzyme, an RNA processing activity that hydrolyzes the 2'-5'phosphodiester linkage at the branchpoint of excised intron lariats. InSaccharomyces cerevisiae, debranching enzyme plays a requisite role in the rapid turnover of excised introns, yet its function is not essential for viability.
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