Spliceosome disassembly catalyzed by Prp43 and its associated components Ntr1 and Ntr2

  1. Rong-Tzong Tsai1,4,
  2. Ru-Huei Fu1,4,
  3. Fu-Lung Yeh1,4,
  4. Chi-Kang Tseng1,3,
  5. Yu-Chieh Lin1,2,
  6. Yu-hsin Huang1, and
  7. Soo-Chen Cheng1,2,3,5
  1. 1Institute of Molecular Biology, and 2Taiwan International Graduate Program, Molecular and Cellular Biology, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China; 3Institute of Microbiology and Immunology, National Yang-Ming University, Shih-Pai, Taipei, Taiwan 112, Republic of China

Abstract

Two novel yeast splicing factors required for spliceosome disassembly have been identified. Ntr1 and Ntr2 (NineTeen complex-Related proteins) were identified for their weak association with components of the Prp19-associated complex. Unlike other Prp19-associated components, these two proteins were primarily associated with the intron-containing spliceosome during the splicing reaction. Extracts depleted of Ntr1 or Ntr2 exhibited full splicing activity, but accumulated large amounts of lariat-intron in the spliceosome after splicing, indicating that the normal function of the Prp19-associated complex in spliceosome activation was not affected, but spliceosome disassembly was hindered. Immunoprecipitation analysis revealed that Ntr1 and Ntr2 formed a stable complex with DExD/H-box RNA helicase Prp43 in the splicing extract. Ntr1 interacted with Prp43 through the N-terminal G-patch domain, with Ntr2 through a middle region, and with itself through the carboxyl half of the protein. The affinity-purified Ntr1–Ntr2–Prp43 complex could catalyze disassembly of the spliceosome in an ATP-dependent manner, separating U2, U5, U6, NTC (NineTeen Complex), and lariat-intron. This is the first demonstration of physical disassembly of the spliceosome, catalyzed by a complex containing a DExD/H-box RNA helicase and two accessory factors, which might function in targeting the helicase to the correct substrate.

Keywords

Footnotes

  • Supplemental material is available at http://www.genesdev.org.

  • Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1377405.

  • 4 These authors contributed equally to this work.

  • 5 Corresponding author.

    5 E-MAIL mbscc{at}ccvax.sinica.edu.tw; FAX 886-2-27883296.

    • Accepted October 28, 2005.
    • Received September 21, 2005.
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