Delete and repeat: a comprehensive toolkit for sequential gene knockout in the budding yeast Saccharomyces cerevisiae.

Gene inactivation is an essential step in the molecular dissection of gene function. In the yeast Saccharomyces cerevisiae, many tools for gene disruption are available. Gene disruption cassettes comprising completely heterologous marker genes flanked by short DNA segments homologous to the regions to the left and right of the gene to be deleted mediate highly efficient one-step gene disruption events. Routinely, in more than 50% of analyzed clones, the marker cassette is integrated in the targeted location. The inclusion of loxP sites flanking the disruption marker gene allows sequence-specific Cre recombinase-mediated marker rescue so that the marker can be reused to disrupt another gene. Here, we describe a comprehensive toolbox for multiple gene disruptions comprising a set of seven heterologous marker genes including four dominant resistance markers for gene disruption, plus a set of Cre expression plasmids carrying eight different selection markers, four of them dominant.