Selection of specific gene probes by combined use of low-stringency PCR amplification and Southern-blot hybridization.

We have developed a protocol to isolate a gene from which only limited (amino-acid) sequence information is available. It involves two PCR amplifications using one constant primer and a set of nested primers and subsequent crosswise Southern hybridization. The amplified DNA giving a signal in both lanes is further processed for use in gene bank screening by applying standard procedures. In this way the structural gene for a thiol protease, BLH1, the homologue of the bleomycin A (a cancerostatic drug) resistance gene of rabbit (and man), was isolated from yeast genomic DNA.