blm3-1 is an allele of UBP3, a ubiquitin protease that appears to act during transcription of damaged DNA.

Yeast Blm10 and mammalian PA200 proteins share significant sequence similarity and both cap the ends of 20 S proteasomes and enhance degradation of some peptide substrates. Blm10 was identified as a suppressor of the yeast blm3-1 mutation, and initially was thought to be the Blm3 protein. Both the blm3-1 and ...
blm10-Delta mutations were reported to cause sensitivity to bleomycin and other forms of DNA damage, suggesting a role for Blm10/PA200-proteasome complexes in DNA repair. We have been unable to observe significant DNA damage sensitivity in blm10-Delta mutants in several genetic backgrounds, and we have therefore further investigated the relationship between BLM10 and blm3-1. We find that blm3-1 is a nonsense mutation in the ubiquitin protease gene UBP3. Deleting UBP3 causes phenotypes similar to those caused by blm3-1, but neither causes a general defect in DNA repair. Ubp3 has several known functions, and genetic interaction data presented here suggest an additional role in transcriptional elongation. The phenotypes caused by blm3-1 and ubp3-Delta mutations are not suppressed by over-expression of BLM10, nor are they affected by deletion of BLM10. These results remove key components of the previously reported connection between Blm10/PA200-proteasome complexes and DNA repair, and they suggest a novel way to interpret sensitivity to bleomycin as resulting from defects in transcription elongation.
Mesh Terms:
Alleles, Animals, DNA Damage, DNA Repair, Endopeptidases, Gene Dosage, Gene Silencing, Humans, Membrane Proteins, Mutation, Nucleic Acid Synthesis Inhibitors, Phenotype, Phleomycins, Proteasome Endopeptidase Complex, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription, Genetic
J. Mol. Biol.
Date: Oct. 27, 2006
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