Identification of the transcribing DNA strand for the deoxynucleotide kinase gene of bacteriophage T2

Abstract

A modified procedure was developed which allows RNA--DNA hybridization reactions to be performed without the loss in translational capacity of mRNA which accompanies hybridization at elevated temperatures or in the presence of the denaturing agent formamide. Separated l and r strands of bacteriophage T2 DNA were hybridized in the presence of 4 M sodium perchlorate at 37 degrees C with total RNA from infected cells. After passage of the hybridization mixture through a nitrocellulose column to remove single-strand DNA and DNA--RNA hybrids, the eluent was measured for its capacity to promote deoxynucleotide kinase (gene 1) synthesis in an in vitro protein-synthesizing system derived from uninfected Escherichia coli. With this procedure, which should be of general use for any message whose product can be measured either enzymatically, immunologically, or by location in an acrylamide gel, it was demonstrated that deoxynucleotide kinase mRNA is transcribed from the l strand of bacteriophage T2 DNA. By titrating with l strand DNA, the number of deoxynucleotide kinase transcripts present 9 min after T2 phage infection at 30 degrees C was estimated to be about 38 copies per cell.