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The autoantigen La/SSB: detection on and uptake by mitotic cells
M Bachmann1, T Zaubitzer, W E Müller
1Institut für Physiologische Chemie, Johannes-Gutenberg Universität, Mainz, Germany.
Experimental Cell Research
|August 1, 1992
Summary
Nuclear autoantigen La protein can enter living mitotic cells and localize within the nucleus, forming speckles. This uptake and nuclear import of La protein can be studied using confocal microscopy.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The nuclear autoantigen La (also known as Sjogren's syndrome antigen A1) is a transcription and termination factor for RNA polymerase III.
- Previous studies indicated that La protein translocalizes to the cell surface of growth-stimulated cells during the G0 to G1 phase transition.
Purpose of the Study:
- To investigate the uptake and intracellular localization of La protein in living mitotic cells.
- To examine the assembly and nuclear import of exogenous La protein in synchronized mitotic cells.
Main Methods:
- Staining of living mitotic cells using the anti-La monoclonal antibody La11G7.
- Addition of La protein to cell culture medium to assess uptake into synchronized mitotic cells.
- Confocal laser scanning microscopy (cLSM) to visualize intranuclear localization of La protein.
Main Results:
- La protein added to the medium was taken up by synchronized mitotic cells, an process inhibited by the anti-La monoclonal antibody.
- In prophase cells, internalized La protein formed a fibrillar network.
- In anaphase/telophase cells, La protein was preferentially transported into newly forming or formed nuclei.
- Intranuclear La protein was observed in the nucleoplasm and assembled into nuclear speckles, some of which encircled the nucleolus.
Conclusions:
- Exogenous La protein can be imported into the nuclei of living mitotic cells.
- The uptake and nuclear import of La protein provide a method to study its intranuclear localization in real-time.
- La protein exhibits distinct intracellular localization patterns within mitotic cells, including nucleoplasmic distribution and association with nuclear speckles.