Transcription Termination Signals in the Nin Region of Bacteriophage Lambda: Identification of Rho-Dependent Termination Regions

AUTOR(ES)

Cheng, SWC.

RESUMO

The ~3-kb nin region of bacteriophage λ, located between genes P and Q contains transcription termination signals as well as 10 open reading frames. Deletions in the nin region frees phage growth from dependence on the λ-encoded N-transcription antitermination system, conferring a Nin phenotype (N-independence). A subregion of nin, roc, is defined by a 1.9-kb deletion (δroc) which partially frees λ growth from the requirement for N antitermination. The roc region has strong transcription termination activity as assayed by a plasmid-based terminator testing system. We report the following features of the roc region: the biologically significant terminators in the roc region are Rho dependent, deletion analysis located the biologically significant termination signals to a 1.2 kb-segment of roc, and analysis of other deletions and point mutations in the roc region suggested at least two biologically significant regions of termination, tR3 (extending from bp 42020 to 42231) and tR4 (extending from bp 42630 to 42825).

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