Translation repression by an RNA polymerase elongation complex

Abstract

SummaryBacteriophage l l l l N and bacterial Nus proteins together with a unique site NUT in the leader of the early viral N gene transcript bind RNA polymerase (RNAP) and form a highly processive antitermination complex; N bound at NUT also represses N translation. In this study, we investigate whether N and NUT cause N translation repression as part of the antitermination complex by testing conditions that inhibit the formation of the N-modified transcription complex for their effect on N-mediated translation repression. We show that nus and nut mutations that in combination destabilize multiple interactions in the antitermination complex prevent N-mediated translation repression. Likewise, transcription of the nut-N region by T7 RNAP, which does not lead to the assembly of an effective antitermination complex when N is supplied, eliminates translation repression. We also demonstrate that a unique mutant b b b b subunit of RNAP reduces N-mediated translation repression, and that overexpression of transcription factor NusA suppresses this defect. We conclude that the N-modified RNAP transcription complex is necessary to repress N translation.

RNA-binding specificity of E. coli NusA

“…In addition to greater anti-termination efficiency, the requirement for λN and BoxB allows regulation of λ anti-termination. Thus, λ N levels are controlled at the levels of transcription, translation and protein stability (45,46). …”

Bacteriophage λ N protein inhibits transcription slippage by Escherichia coli RNA polymerase

“…Mutant β subunits (encoded by rpoB ) of E. coli RNAP exist that increase or decrease the frequency of transcriptional slippage (8). One of the β mutants, P564L, demonstrated increased slippage and showed a defect in the formation of transcription antitermination complexes with the N protein of bacteriophage λ (16–18). …”

A New Look at Bacteriophage λ Genetic Networks

“…BoxA RNA binds the NusB and NusE complex (43,46). Thus, N, Nus factors, and Nut RNA interact with RNA Pol while tethered by the nascent RNA transcript (44,(66)(67)(68) (Fig. 3).…”

“…3). N and RNase III act at their respective binding sites to repress and enhance N translation, respectively (67,68). When RNA Pol first transcribes the pL operon after phage infection, it transcribes through the N gene and terminates at tL1 (Fig.…”