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Updated: May 24, 2026

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC
Published on: May 9, 2020
Spatiotemporal behavior of nuclear cyclophilin B indicates a role in RNA transcription
Birger Dieriks1, Patrick Van Oostveldt
1Department of Molecular Biotechnology, Ghent University, Ghent, Belgium. birger.dieriks@gmail.com
Abstract:
Cyclophilin B (CypB) is an ubiquitously expressed protein, which performs several intra- and extracellular functions. Despite its abundant use as a household protein, little is known about its exact cellular localization and dynamics. In the present study we show that endogenous CypB localizes in one of two distinct compartments, either within the endoplasmic reticulum (ER) or inside the nucleus, accumulating in the fibrillar centers of the nucleoli. By means of a genetic deletion screen, we identified a minimal nucleolar localization signal for efficient relocation to the nucleoli. Within the fibrillar centers, CypB colocalized with RNA polymerase, upstream binding factor-1 (UBF), fibrillarin and dyskerin (DCK1). Even after chemical disruption of the nucleoli, a strong interaction with these proteins remained. Using live cell imaging, we showed a persistent colocalization of CypB with proteins involved in the ribosome biogenesis during the transcriptionally more active phases of the cell cycle. Supported by in silico data, our observations suggest that CypB interacts with these proteins and is involved in ribosome biogenesis and RNA transcription.
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