Isolation and characterization of KIUBP2, a ubiquitin hydrolase gene of Kluyveromyces lactis that can suppress a ts-mutation in CBF2, a gene encodinga centromeric protein of Saccharomyces cerevisiae

The Kluyveromyces lactis UBP2 gene was isolated as a suppressor of a temper ature-sensitive mutation in CBF2, a gene coding for 3 centromere-binding pr otein of Saccharomyces cerevisiae. The UBP genes are hydrolases than can cl eave a ubiquitin moiety from a protein substrate. KlUBP2 is not essential f or growth since a disruption of the KlUBP2 gene had little effect, except f or a slight decrease in the growth rate. The stability of centromere-contai ning plasmids was not influenced either. In addition to klUBP2, five S. cer evisiae genes involved in the ubiquitination pathway could suppress the ts- mutation in the CBF2 gene, namely UBA1, UBA2, UBP1, UBP2 and YUH1, although YUH1 was the only one that could do this like KlUBP2 from a single-copy pl asmid. Surprisingly, these genes encode pl otc ins with antagonistic activi ty as two, UBA1 and UBA2, are ubiquitin-activating enzymes whereas the othe r three are de-ubiquitinating hydrolases.