Localisation and characterization of a new rho-dependent transcription terminator from bacteriophage T5

Relatively few rho-dependent terminators have been described in the literature. This manuscript describes another such terminator, isolated from phage T5. Functional analysis, involving the generation of deletion subclones, has permitted the localization of the terminator on a 413 bp fragment. Attempts to further reduce the size of this fragment resulted in loss of terminator activity. DNA sequence analysis of the terminator region supports the model whereby a rho-dependent terminator is composed of a long region of non-translated unstructured DNA, which permits rho binding, followed by RNA polymerase pausing sites where termination (in the presence of rho) may occur. The results agree with the currently held hypothesis that, despite the many similarities found between various rho dependent termination sequences, no consensus can be defined for either the rho binding or the rho termination sites (1,2).