Transcription in vitro of bacteriophage lambda 4S RNA: studies on termination and r±LQ protein

When bacteriophage Xpgal8 DNA is transcribed in a purified in _ vitro system by E_. coli RNA polymerase (nucleoside triphosphate: RNA nucleotidyl-transferase, EC 2.7.7.6), several major transcripts are synthesized. We have investigated transcriptional termination of one of these transcripts, the 4S, or "oop " RNA. Analysis by two-dimensional "fingerprinting " of Tl oligonucleotides reveals that transcription of the 4S RNA terminates at a specific site on the Xpgal8 DNA template, t, ' with an efficiency of approximately 80Z, i.e. 20X of transcripts are extended into larger RNAs. Addition of the E. coli protein rho to our transcription reactions has two effects: a) the efficiency of termination at the t, ' site is Increased to 1001; b) the number of AS transcripts synthesized is increased by greater than 5-fold. Rho appears to stimulate 4S RNA synthesis by facilitating more rapid release of RNA polymerase from the t, ' termination site