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Microtubule-associated protein-2 stimulates DNA synthesis catalyzed by the nuclear matrix
M Shioda1, H Murofushi, K Murakami-Murofushi
1Department of Physiological Chemistry and Nutrition, Faculty of Medicine, Tokyo, Japan.
Abstract:
Microtubule-associated protein-2 (MAP-2) isolated from porcine brains stimulated DNA synthesis catalyzed by the nuclear matrix isolated from Physarum polycephalum in the presence of activated DNA as exogenous templates. The degree of the stimulation depended on the amount of the nuclear matrix, but not on that of the template. MAP-2 also stimulated DNA polymerase alpha activity solubilized from nuclei, but not DNA polymerase beta activity. These results suggest that MAP-2 stimulates DNA synthesis by interacting with the putative DNA replication machinery including DNA polymerase alpha bound to the matrix. Similar stimulation occurred in the nuclear matrix isolated from HeLa and rat ascites hepatoma cells, which strongly suggests that MAP-2 is involved in the control of DNA replication in eukaryotic cells.
Insights
Microtubule-associated protein-2 (MAP-2) from porcine brains enhances DNA synthesis in eukaryotic cell nuclear matrices. This protein specifically stimulates DNA polymerase alpha, suggesting a role in regulating DNA replication.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The nuclear matrix plays a crucial role in organizing DNA and is involved in DNA replication.
- Microtubule-associated protein-2 (MAP-2) is a protein primarily known for its role in microtubule stabilization.
- Understanding the regulatory mechanisms of DNA synthesis is fundamental to cell biology.
Purpose of the Study:
- To investigate the effect of Microtubule-associated protein-2 (MAP-2) on DNA synthesis.
- To determine if MAP-2 interacts with nuclear matrix components involved in DNA replication.
- To explore the potential role of MAP-2 in the control of eukaryotic DNA replication.
Main Methods:
- Isolation of nuclear matrix from Physarum polycephalum, HeLa cells, and rat ascites hepatoma cells.
- Assaying DNA synthesis using activated DNA as exogenous templates in the presence of isolated nuclear matrices.
- Measuring the activity of solubilized DNA polymerase alpha and DNA polymerase beta.
Main Results:
- MAP-2 significantly stimulated DNA synthesis catalyzed by the nuclear matrix, with stimulation dependent on the amount of nuclear matrix.
- MAP-2 enhanced the activity of DNA polymerase alpha but not DNA polymerase beta.
- Similar stimulatory effects were observed using nuclear matrices from different eukaryotic cell types (HeLa and rat ascites hepatoma).
Conclusions:
- MAP-2 appears to play a role in stimulating DNA synthesis by interacting with the DNA replication machinery, particularly DNA polymerase alpha, associated with the nuclear matrix.
- The findings suggest that MAP-2 is involved in the regulation of DNA replication across various eukaryotic cells.
- This study highlights a novel function for MAP-2 beyond its known role in microtubule dynamics.