Binding of Transcription Termination Protein Nun to Nascent RNA and Template DNA

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Science  17 Dec 1999:
Vol. 286, Issue 5448, pp. 2337-2339
DOI: 10.1126/science.286.5448.2337

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The amino-terminal arginine-rich motif of coliphage HK022 Nun binds phage λ nascent transcript, whereas the carboxyl-terminal domain interacts with RNA polymerase (RNAP) and blocks transcription elongation. RNA binding is inhibited by zinc (Zn2+) and stimulated by Escherichia coli NusA. To study these interactions, the Nun carboxyl terminus was extended by a cysteine residue conjugated to a photochemical cross-linker. The carboxyl terminus contacted NusA and made Zn2+-dependent intramolecular contacts. When Nun was added to a paused transcription elongation complex, it cross-linked to the DNA template. Nun may arrest transcription by anchoring RNAP to DNA.

  • * Present address: Whitehead Institute, 9 Cambridge Center, Cambridge, MA 02142, USA.

  • To whom correspondence should be addressed. E-mail: gottesma{at}

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