Restriction enzymes were obtained from Promega (Madison, WI, USA), MBI Fermentas (Vilnius, Lithuania) and Roche Applied Science (Indianapolis, IN, USA). The QuikChange XL II site-directed specific mutagenesis kit was purchased from Stratagene (La Jolla, CA, USA). DNA sequencing was performed by Genewiz (Germantown, MD, USA). Escherichia coli DH5a was used to amplify plasmid DNA. Transformation of yeast and E. coli and were performed as previously described (19) . YPAD, SD and 4.7 MB plates for testing the killer phenotype were as previously reported (19) . Plasmids for expression of dual luciferase reporters were described previously (20) .