CONSTRUCTION OF A NORMALIZED CDNA LIBRARY BY INTRODUCTION OF A SEMISOLID MESSENGER-RNA-CDNA HYBRIDIZATION SYSTEM

We report a novel procedure to construct a normalized (equalized) cDNA library. By introduction of the highly efficient self-hybridization s ystem between a whole mRNA population and their corresponding cDNA imm obilized on latex beads; which involves relatively simple manipulation s, we were able to generate an mRNA population in which the copy numbe r of abundant species was reduced while that of rare species was enric hed. In a typical experiment, after several cycles of self-hybridizati on on the beads, the ratio of the most to the least abundant marker mR NA species dropped by a factor of 300 (from 10,000 to 30) while the co mplexity and length of mRNAs in the population remained unchanged. The procedure should provide a potent tool for the expression cloning of cDNA and also facilitate the construction of whole cDNA catalogues fro m specific tissues (or cell types) from higher organisms.