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Mitochondrial protein p32 can accumulate in the nucleus
K A Brokstad1, K H Kalland, W C Russell
1Broegelmann Research Laboratory, University of Bergen, Bergen, N-5021, Norway.
Biochemical and Biophysical Research Communications
|March 13, 2001
Summary
Human p32 protein, usually in mitochondria, moves to the nucleus when cells are treated with specific drugs. This study identifies regions of p32 involved in its nuclear import and export.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The human p32 protein was initially identified in association with the splicing factor ASF/SF-2.
- p32 is synthesized as a pre-protein, with a mitochondrial import signal cleaved to yield mature p32, predominantly localized in mitochondria.
Purpose of the Study:
- To investigate the extramitochondrial localization of human p32.
- To understand the mechanisms governing the nuclear import and export of p32.
Main Methods:
- Treatment of cells with leptomycin B or actinomycin D to induce nuclear localization of endogenous p32.
- Cloning of mature p32 and its deletion mutants into enhanced green fluorescence protein (EGFP) reporter plasmids.
- Transfection of COS cells with EGFP-p32 constructs and analysis of protein localization via fluorescence microscopy.
Main Results:
- Endogenous p32 showed increased nuclear localization upon treatment with leptomycin B or actinomycin D.
- Transfected EGFP-p32 was primarily found in the cytoplasm, with some nuclear presence.
- Drug treatment caused EGFP-p32 to accumulate in the nucleus, indicating drug-sensitive transport.
- Deletion analysis pinpointed specific regions of p32 responsible for nuclear import and export.
Conclusions:
- Human p32 exhibits dynamic extramitochondrial localization, including nuclear import.
- The nuclear import and export of p32 are regulated processes influenced by cellular treatments.
- Specific domains within the p32 protein mediate its transport between the cytoplasm and nucleus.