Here we describe a new strategy for cDNA library construction, in which the random primers directing the first strand cDNA synthesis contain additional d (AC) at their 5'-ends, and the linkers which will be added to the double strand cDNA contain d(GTCG) at the 5′-ends. When the linker is added to the 3'-end of the cDNA, a complete SalI
site d(GTCGAC) will form at the 3'-end but not at the 5′-end of the cDNA fragment. After SalI
digestion, the 3'-cohesive and the pre-existing 5'Eco
RI cohesive ends are used to introduce the double stranded cDNA into the linearized plasmid vectors. The ligation products were used to transform E.coli
to produce a cDNA library. Using this method, we constructed a directional Xenopus laevis
embryonic cDNA library for yeast two-hybrid. We checked the ratio of empty vectors, the size of inserts and existence of several genes, the results showed that cDNA library construction was successful.