Analysis of rabbit brain polysomal poly (A+) mRNA by DNA excess hybridization

DNA sequence representation in rabbit brain mRNA was examined by DNA excess hybridization. purified polysomal poly (A+) mRNA was labeled in vitro with [3H] dimethyl sulfate and reacted at DNA: RNA ratios of 5000 : 1 and 30 000 : 1. Poly(A+) mRNA hybridizied mainly to nonrepeated DNA with a smaller kinetic component which was complementary to repeated DNA sequences. The latter component was not due to nuclear or ribosomal RNA contamination. Poly(A-) RNA purified from brain polysomes hybridized to excess DNA as a single repeated component. Thermal denaturation profiles of the RNA - DNA hybrids indicated a high degree of fidelity in base pairing.