title: blm3-1 is an allele of UBP3, a ubiquitin protease that appears to act during transcription of damaged DNA.
abstract: 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.
authors.affiliation: University of Utah School of Medicine, Department of Biochemistry, 15 N Medical Drive East RM 4100, Salt Lake City, UT 84112-5640, USA.
authors.forename: Shannon
authors.initials: S
authors.lastname: McCullock
authors.forename: Todd
authors.initials: T
authors.lastname: Kinard
authors.forename: Laura
authors.initials: L
authors.lastname: McCullough
authors.forename: Tim
authors.initials: T
authors.lastname: Formosa
mesh_terms: D000483:Alleles; D000818:Animals; D004249:DNA Damage; D004260:DNA Repair; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D020868:Gene Silencing; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D019384:Nucleic Acid Synthesis Inhibitors / Q000378:metabolism; D010641:Phenotype; D010692:Phleomycins; D046988:Proteasome Endopeptidase Complex; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C500597:Blm10 protein, S cerevisiae; D008565:Membrane Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D010692:Phleomycins; D029701:Saccharomyces cerevisiae Proteins; D010450:Endopeptidases; D046988:Proteasome Endopeptidase Complex; C101111:UBP3 protein, S cerevisiae