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CPP: Chemische Physik und Polymerphysik

CPP 17: Poster: Spectroscopy and Single Particle Spectroscopy of Molecular Systems, Photoprocesses, Biological Systems

CPP 17.9: Poster

Dienstag, 3. April 2001, 12:30–15:00, AT1

MOBILITY OF SINGLE U1 snRNP WITHIN THE CELL NUCLEUS — •Thorsten Kues¹, Achim Dickmanns², Reiner Peters¹, Reinhard Lührmann², and Ulrich Kubitscheck¹ — ¹Institut für Med. Physik und Biopysik, Westfälische Wilhelms-Universität, Münster — ²Zelluläre Biochemie, MPI für biophysikalische Chemie, Göttingen

The U small nuclear ribonucleoproteins (U snRNPs) are components of the splicing complexes that remove introns from pre-mRNA in the cell nucleus. We have studied the intranuclear movements of U1 snRNP particles within cell nuclei on a single molecule level using dual color high speed and high sensitivity laser microscopic methods. U1 snRNP particles were fluorescently labeled with Alexa 488 or Cy5, and imported into nuclei of digitonin semi-permeabilized 3T3 mouse cells in a signal dependent manner. Images taken on a millisecond time scale were further processed using especially developed image analysis tools. Analysis of the single molecule trajectories revealed that U1 snRNPs were slowly moving (D < 0.25 µm²/s) when residing in special nuclear regions, which corresponded presumably to speckles. Within speckles the molecules could be localized with an accuracy of < 20 nm. U1 snRNPs remained in speckles only for a limited time that was characterized by a decay time of 200 ms. Our data indicate a restricted mobility of nuclear splicing factors within speckles for the first time on a single molecule level.