Rho Factor Function in T4 RNA Transcription

polymerase from Escherichia coli is strongly influenced by the protein factors sigma (~) and rho (p). Sigma directs the initiation of RNA chains at specific sites on the DNA templates (Burgess et al., 1969; Travers and Burgess, 1969) and p causes the termination and release of RNA mole-cules during transcription i vitro (Roberts, 1969). Unlike a, however, pis not isolated with the enzyme and has therefore been absent from most reaction mixtures used previously to study RNA polymerase activity. This paper reports on the effect of p factor on transcription of T4 DNA in vitro. Two classes of RNA molecules can be readily distinguished among the species appearing during transcription of T4 DNA in vivo before replication: