Magnetic bead capture of cDNAs from double-stranded plasmid cDNA libraries

We have developed a cDNA library screening method which allows the simultaneous screening of >10(12) double-stranded plasmid cDNA molecules with minimal a priori sequence knowledge. A biotinylated, gene-specific oligonucleotide probe along with abutting 'blocking' oligos is hybridized to the plasmid cDNA library and the target plasmid retrieved with paramagnetic streptavidin beads and transformed into Escherichia coli. Multiple rounds of enrichment with a target plasmid represented at 0.002-0.0001% resulted in over one-third positive clones. Our method will be useful for isolating even the rarest cDNAs starting from ESTs, isolated exons or homologous sequence information.