Assay of DNA-RNA hybrids by S1 nuclease digestion and adsorption to DEAE-cellulose filters

摘要

A fast and accurate assay procedure for DNA-RNA hybrids is described in which exhaustive digestion of unhybridized DNA with S₁ nuclease is followed by binding of hybrids to filter discs of DEAE-cellulose. The digested DNA can be efficiently washed from the filters so that background levels of 0.1–0.2% of input tracer DNA can be achieved, in contrast to the much higher (～1–5%) backgrounds obtained using TCA precipitation procedures. Short duplexes, as small as 36 nucleotides in length, which are inefficiently bound to hydroxyapatite, are quantitatively bound to the DEAE-cellulose filters.