ACCELERATED SCREENING OF CDNA LIBRARIES USING THE POLYMERASE CHAIN-REACTION AND SOUTHERN BLOTTING

cDNA libraries are normally constructed in either phage or' plasmid ve ctors and screened for sequences of interest using antibodies or, more commonly, nucleic acid probes. To clone a sequence of interest from a library generally involves at least thr ee rounds of hybridization wi th P-32-labeled probes. This approach is highly labor intensive, and n o information about the size of the hybridizing insert is obtained unt il the clones have been purified and the insert DNA analyzed by restri ction enzyme digestion. WE report On a rapid screening protocol for li braries constructed in bacteriophage lambda vectors involving polymera se chain reaction amplification of the insert from hybridizing phage p laques and on its analysis by agarose gel electrophoresis and Southern blotting. This can take place after only one round of conventional sc reening, and phage fi om a large number of positively hybridizing plaq ues can be analyzed by a ''one-tube'' reaction.