The Bacillus subtilis RNA polymerase bound to phage φ29 DNA has been visualized by electron microscopy. Seven specific binding sites have been observed at 1.7(±0.4)†, 25.5(±0.5), 26.7(±0.4), 59.4(±1.2), 79.3(±0.9), 91.3(±0.6) and 99sd3(± 0.4) DNA length units (one unit is equal to 1% of the length of φ29 DNA). Three of the sites are located in fragment EcoRI A, two in fragment EcoRI B and two in fragment EcoRI C. The same binding sites are seen whether proteinase K-treated φ29 DNA or protein p3-containing φ29 DNA is used. By hybridization of early or late φ29 induced RNA, at saturation, to the separated strands of uniformly labelled φ29[32P]DNA restriction fragments, which cover more than 95% of the genome, we have determined the extent of the in vivo early transcription from the L strand of fragments EcoRI A, B and D and HpaII C and that of late transcription from the complementary strands (H strand). We have shown the existence of symmetric transcription within most of fragment EcoRI B and in about one third of fragment EcoRI D. We have also found that sus mutants in cistron 4 do not induce the synthesis of late RNA suggesting that protein p4 is involved in the control of late transcription.

This investigation has been aided by grants from Comisión Asesora para el Desarrollo de la Investigaci6n Cientifica y Técnica, Comisión Administradora de1 Descuento Complc- mentario (I. N. P.) and Dirección General de Sanidad. One of us (M. R. I.) Is a Fellow of the Juan March Foundation.

Peer reviewed