Article

Localization of Prp8, Brr2, Snu114 and U4/U6 proteins in the yeast tri-snRNP by electron microscopy.

Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.
Nature Structural & Molecular Biology (Impact Factor: 11.63). 11/2008; 15(11):1206-12. DOI: 10.1038/nsmb.1506
Source: PubMed

ABSTRACT The U4/U6-U5 tri-small nuclear ribonucleoprotein (snRNP) is a major, evolutionarily highly conserved spliceosome subunit. Unwinding of its U4/U6 snRNA duplex is a central event of spliceosome activation that requires several components of the U5 portion of the tri-snRNP, including the RNA helicase Brr2, Prp8 and the GTPase Snu114. Here we report the EM projection structure of the Saccharomyces cerevisiae tri-snRNP. It shows a modular organization comprising three extruding domains that contact one another in its central portion. We have visualized genetically tagged tri-snRNP proteins by EM and show here that U4/U6 snRNP forms a domain termed the arm. Conversely, a separate head domain adjacent to the arm harbors Brr2, whereas Prp8 and the GTPase Snu114 are located centrally. The head and arm adopt variable relative positions. This molecular organization and dynamics suggest possible scenarios for structural events during catalytic activation.

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