The remarkable specificity of a new transcription termination factor suggests that the mechanisms of termination and antitermination are similar

Robert, J. Lake; Sloan, Sleghild Böhmer; Weisberg, Robert A.; Gottesman, Max E.; Robledo, Renato; Harbrecht, Douglas F.

doi:10.1016/0092-8674(87)90644-1

Cited by 73 publications

(87 citation statements)

References 35 publications

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“…However, we remind the reader that the nun gene, while occupying a position on the HK022 genome analogous to the position of N on the X genome, does not appear to function as an antitermination protein (Robert et aL, 1987). Although there is no evidence that HK022 has an antitermination function analogous to X N, there are sites downstream of the early promoters that have similar sequences and are required for transcription antitermination.…”

Section: Antitermination In Hk022mentioning

confidence: 94%

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Transcription antitermination: the λ paradigm updated

Friedman

Court²

1995

Molecular Microbiology

128

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Section: Antitermination In Hk022mentioning

confidence: 94%

“…Mutations in Escherichia coil nus genes that cause a failure in N-mediated antitermination also affect Nun-mediated termination (Robert et aL, 1987;Robledo et aL, 1990). Moreover, other mutations in these nus genes have been isolated that reduce Nun action but not N action (Robledo et aL, 1991).…”

Section: Hk022 Nun Proteinmentioning

confidence: 99%

Transcription antitermination: the λ paradigm updated

Friedman

Court²

1995

Molecular Microbiology

128

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“…The 13-kD Nun protein, like the N antitermination protein, binds to the cis-acting nut RNA elements through an arginine-rich binding motif (Chattopadhyay et al 1995). In contrast to N, which suppresses transcription termination promoter-distal to nut, Nun provokes termination downstream of these elements in both the p L and p R operons (Robert et al 1987;Robledo et al 1990;Sloan and Weisberg 1993). Nun-induced transcription termination is inhibited by mutations in nut or in the trans-acting Escherichia coli proteins NusA, NusB, NusE, and NusG (Robert et al 1987;Robledo et al 1990Robledo et al , 1991Baron and Weisberg 1992;E.…”

mentioning

confidence: 99%

“…The product of the nun gene of prophage HK022 inhibits superinfection by the related coliphage (Robert et al 1987). The 13-kD Nun protein, like the N antitermination protein, binds to the cis-acting nut RNA elements through an arginine-rich binding motif (Chattopadhyay et al 1995).…”

mentioning

confidence: 99%

The Nun protein of bacteriophage HK022 inhibits translocation of Escherichia coliRNA polymerase without abolishing its catalytic activities

Hung¹,

Gottesman²

1997

Genes Dev.

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Bacteriophage HK022 Nun protein blocks transcription elongation by Escherichia coli RNA polymerase in vitro without dissociating the transcription complex. Nun is active on complexes located at any template site tested. Ultimately, only the 3 -OH terminal nucleotide of the nascent transcript in an arrested complex can turn over; it is removed by pyrophosphate and restored with NTPs. This suggests that Nun inhibits the translocation of RNA polymerase without abolishing its catalytic activities. Unlike spontaneously arrested complexes, Nun-arrested complexes cannot be reactivated by transcription factor GreB. The various complexes show distinct patterns of nucleotide incorporation and pyrophosphorolysis before or after treatment with Nun, suggesting that the configuration of RNAP, transcript, and template DNA is different in each complex.

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“…The only known role of Nun is to exclude superinfecting λ and phage λ imm 434 , which have the same NUT sites. 60 Nun does so both by competing with λN for binding to the BoxB stem loop of the NUT RNA sites within the nascent λ transcript 61 and by arresting transcription at pause sites on the λ chromosome. 62 λ N antitermination…”

Section: Phage Proteins That Affect Transcription Elongation: λ N λ mentioning

confidence: 99%

Transcription elongation

2017

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This review is focused on recent progress in understanding how Escherichia coli RNAP polymerase translocates along the DNA template and the factors that affect this movement. We discuss the fundamental aspects of RNAP translocation, template signals that influence forward or backward movement, and host or phage factors that modulate translocation. Mechanism of transcription elongationTernary elongation complex (TEC) assembled by DNA template, RNA polymerase and emerging RNA product is the principal intermediate of transcription (Fig. 1). During the elongation step of RNA synthesis, the RNA product remains transiently base-paired to the template DNA strand, forming 9-10 bp RNA: DNA hybrid, 1 whereas the other DNA strand is separated from the template (Fig. 1). The resulting melted DNA region of 10-12 nt 2,3 is called the "transcription bubble." The crucial nucleic acid-protein interactions in TEC involve three principal functionally and structurally defined elements. 4 One of these, the downstream DNA binding site, encloses downstream DNA duplex and acts as a sliding clamp, whereas the two other sites resemble zip locks operationally. The rear zip lock clasps the upstream edge of the RNA:DNA hybrid and ensures displacement of RNA product from template during elongation, whereas the front zip lock, which coincides with RNAP active center, secludes the downstream boundary of the hybrid and also enables peeling of RNA from DNA upon backtracking RNAP. 1,5,6 Both front and rear zip locks accommodate the RNA:DNA hybrid in the hybrid binding site and maintain through topological contacts alone a constant configuration of nucleic acid scaffold upon RNAP lateral movement. Most interactions between the nucleic acid scaffold and RNAP in TEC are not sequence-specific. Some preference to dG residues has been demonstrated in the "core recognition element, CRE" of the b subunit (see below). However, these interactions do not seem to significantly affect TEC reactions, only in rare occasions contributing to RNAP escape from pausing. In X-ray structures of TEC, 7,8 the downstream DNA binding site is seen as a deep cleft formed by the b and b 0 subunits (Fig. 1). The RNA:DNA hybrid is accommodated in the main channel at the interface of the same subunits between the b 0 Bridge helix, b Fork loop II and the active center at its downstream end and the b 0 Rudder and b 0 Lid loops at its upstream end, which correspond to the front and rear zip locks respectively. After peeling from the DNA, the synthesized RNA transcript is channeled into an extended narrow cavity formed by the b 0 Lid and b 0 Zn-finger subdomains as well as the "Flap," which is a long flexible b subunit loop.Each individual step of RNA extension by RNA polymerase produces TEC in which the RNA 3 0 end occupies the iC1 site of the enzyme active center

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The remarkable specificity of a new transcription termination factor suggests that the mechanisms of termination and antitermination are similar

Cited by 73 publications

References 35 publications

Transcription antitermination: the λ paradigm updated

Transcription antitermination: the λ paradigm updated

The Nun protein of bacteriophage HK022 inhibits translocation of Escherichia coliRNA polymerase without abolishing its catalytic activities

Transcription elongation

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