Dosage suppression of the Kluyveromyces lactis zymocin by Saccharomyces cerevisiae ISR1 and UGP1.
The Kluyveromyces lactis zymocin complex kills Saccharomyces cerevisiae cells in a process that involves tRNA cleavage by its tRNAse gamma-toxin subunit. In contrast to the gamma-toxin mode of action, the early steps of the zymocin response are less well characterized. Here, we present high-dosage suppressors of zymocin that encode a putative Pkc1-related kinase (ISR1) and UDP-glucose pyrophosphorylase (UGPase) (UGP1). Anti-UGPase Western blots and GAL10 - ISR1 overexpression suggest that zymocin suppression correlates with overproduction of UGPase or Isr1. As judged from protection against exo-zymocin and unaltered sensitivity to endogenous gamma-toxin, high-copy ISR1 and UGP1 operate in early, nontarget steps of the zymocin pathway. Consistent with a recent report on in vitro phosphorylation of Isr1 and UGPase by the CDK Pho85, high-copy ISR1 and UGP1 suppression of zymocin is abolished in a pho85 null mutant lacking CDK activity of Pho85. Moreover, suppression requires UGPase enzyme activity, and ISR1 overexpression also protects against CFW, a chitin-interfering poison. Our data agree with roles for UGPase in cell wall biosynthetic processes and for Isr1 in Pkc1-related cell wall integrity. In sum, high-copy ISR1 and UGP1 cells affect early steps of the zymocin response and potentially prevent the lethal K. lactis killer complex from establishing cell surface recognition and/or contact.
Mehlgarten
Constance
C
Biologicum, Institut für Biologie, Institutsbereich Genetik, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany.
Zink
Sabrina
S
Rutter
Jared
J
Schaffrath
Raffael
R
D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D055646:Killer Factors, Yeast; D007716:Kluyveromyces / Q000235:genetics / Q000378:metabolism*; D009183:Mycotoxins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000235:genetics / Q000378:metabolism*
D000935:Antifungal Agents; D016213:Cyclins; D055646:Killer Factors, Yeast; D009183:Mycotoxins; C090559:PCL2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C058975:zymocin; C061570:protein kinase N; D011493:Protein Kinase C; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase