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Single mRNP tracking in living mammalian cells
Alon Kalo1, Pinhas Kafri, Yaron Shav-Tal
1The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan, Israel.
Abstract:
The translocation of single mRNPs (mRNA-protein complexes) from the nucleus to the cytoplasm through the nuclear pore complex (NPC) is an important basic cellular process. Originally, in order to visualize this process, single mRNP export was examined using electron microscopy (EM) in fixed Chironomus tentans specimens. These studies described the nucleocytoplasmic translocation of huge mRNPs (~30 kb) transcribed from the Balbiani-ring genes. However, knowledge of the in vivo mRNP kinetics in cell compartments remained poor up until recently. The current use of unique fluorescent protein tags, which are able to bind to mRNA transcripts, has allowed the detection and measurements of single mRNP kinetics in living cells. This has demonstrated that mRNP movement is affected by the size of the transcript and the splicing process. It was found that mRNP rates of translocation are slower in the nucleus compared to the cytoplasm and that the cell nucleus contains interchromatin tracks in which mRNPs diffuse. In order to track single mRNP movement in living cells, it is important to be able to identify single mRNP molecules transcribed from a certain gene, at the single-cell level. Single-molecule analysis of gene expression requires advanced imaging systems and analytical software in order to detect and follow the movement of single mRNPs. In this chapter we describe the methods required for the detection and tracking of single mRNP movement in living mammalian cells.
Insights
Tracking single mRNA-protein complexes (mRNPs) in living cells reveals slower nuclear movement compared to the cytoplasm. Advanced imaging methods allow for the detection and measurement of mRNP kinetics, impacting our understanding of gene expression.
Area of Science:
- Cell Biology
- Molecular Biology
- Biophysics
Background:
- Nuclear pore complex (NPC) mediated export of messenger ribonucleoprotein complexes (mRNPs) is crucial for gene expression.
- Early studies used electron microscopy on fixed specimens, limiting in vivo kinetic analysis.
- Recent advances in live-cell imaging have enabled detailed investigation of mRNP dynamics.
Purpose of the Study:
- To describe methods for detecting and tracking single mRNP movement in living mammalian cells.
- To elucidate the kinetics of mRNP translocation within cellular compartments.
- To understand how factors like transcript size and splicing influence mRNP movement.
Main Methods:
- Utilizing fluorescent protein tags to label and visualize individual mRNA transcripts in real-time.
- Employing advanced imaging systems for high-resolution detection of single mRNPs.
- Developing analytical software for precise tracking of mRNP trajectories.
Main Results:
- mRNP translocation rates are significantly slower in the nucleus than in the cytoplasm.
- Nuclear mRNP diffusion occurs within specific interchromatin tracks.
- Transcript size and the splicing process were identified as key factors affecting mRNP kinetics.
Conclusions:
- Live-cell imaging provides unprecedented insights into the in vivo kinetics of mRNP transport.
- Understanding mRNP movement is essential for comprehending the regulation of gene expression.
- The described methods facilitate single-molecule analysis of gene expression in living cells.
