RAPID SCREENING OF AN ARRAYED cDNA LIBRARY BY IMPROVED PCR-BASED METHOD

摘要

Tbe present study reports an improved PCR-based technique that allows quick and effecfive screening of eDNA libraries. First, the eDNA library was arrayed as follows: about 3×106 cDNA clones were multiplied as individual plsques on solid medium in 24-well culture dishes at 1 200 plaque forming units per well.The phage suspension of each well was transferred to an individual micrccentrifuge tube in 72-tube box. Then,box pool, row pools and column pools were set up that respectively represent a 72-tube box,rows and columns within the box. To screen a specific target cDNA,primers specific for novel ESTs obtained in our laboratory were eznployed to conduct PCR in a fiierarchy mode. PCR began with the box pools, resulting in the identification of some positive box pools. Then PCR went down to the row and column pools of the positive box. Tbe intersection of the positive row(s) and column(s) revealed the candidate positive tubes. The specificity of PCR products were meanwhile checked hy restriction enzyme digestion. Finally, hybridization was carried out to get single specific eDNA clones-from the positive tlabes. This PCR-hased technique features high specificity, high efficiency and Les-cost in large-scale cDNA library screening. Our initial implementation of the technique resulted in the isolation of three longer different cDNA clones from a hnman fetal brain eDNA library. Thus this improved technique can serve as an alternative to the time-consuming and laborious conventional hybridization-hased metfiod for screening cDNA library.