Pub1 acts as an E6-AP-like protein ubiquitiin ligase in the degradation of cdc25.
The level of the mitotic activating tyrosine phosphatase cdc25 is regulated by both transcriptional and post-transcriptional mechanisms in the fission yeast Schizosaccharomyces pombe. We have found that cdc25 is ubiquitinated and have cloned pub1, a gene which regulates this event. Pub1 contains a region highly homologous to the putative catalytic domain of the human protein ubiquitin ligase E6-AP. Disruption of pub1 elevates the level of cdc25 protein in vivo rendering cells relatively resistant to the cdc25-opposing tyrosine kinases wee1 and mik1. In addition, loss of wee1 activity in a pub1-disruption background results in a lethal premature entry into mitosis which can be rescued by loss of cdc25 function. A ubiquitin-thioester adduct of pub1 was isolated from fission yeast and disruption of pub1 dramatically reduced ubiquitination of cdc25 in vivo. These results suggest that pub1 directly ubiquitinates cdc25 in vivo.
Nefsky
B
B
Cold Spring Harbor Laboratory, NY 11724, USA.
Beach
D
D
D000595:Amino Acid Sequence; D019731:Carbon-Nitrogen Ligases; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004952:Esters / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014452:Ubiquitins / Q000378:metabolism*; D020687:cdc25 Phosphatases
D018797:Cell Cycle Proteins; D004952:Esters; D005656:Fungal Proteins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; D013438:Sulfhydryl Compounds; D014452:Ubiquitins; C090679:mik1 protein, S pombe; C068689:wee1 protein, S pombe; D011505:Protein-Tyrosine Kinases; D010749:Phosphoprotein Phosphatases; D020687:cdc25 Phosphatases; D008025:Ligases; D019731:Carbon-Nitrogen Ligases; C098922:Pub1 protein, S pombe