Related Experiment Videos
Identification and characterization of a nuclear scaffold protein that binds the matrix attachment region DNA
K Tsutsui1, K Tsutsui, S Okada
1Department of Molecular Biology, Okayama University Medical School Japan.
Abstract:
The association of nuclear DNA with the nuclear matrix (scaffold) is mediated by defined segments of DNA called matrix association region (MAR). By using a plasmid harboring a portion of the Ig kappa gene within which MAR had been located, we searched for proteins recognizing MAR in the nuclear scaffold components electrophoretically separated and blotted onto a membrane. In the presence of nonspecific competitor DNA, the labeled plasmid selectively bound to a protein with apparent molecular weight of 120,000 (designated SP120). The protein was purified directly from SDS-polyacrylamide gels and renatured by a guanidine hydrochloride procedure. The DNA region in the plasmid responsible for the binding to the solubilized SP120 coincided with the 365-base pair HindIII-HinfI fragment that had been identified as MAR. In solution, SP120 exhibited a cooperative mode of interaction with the end-labeled MAR fragment. Measurement of relative affinities of MAR subfragments to SP120 showed that the whole region is required for efficient binding. This is consistent with the minimal length for MAR estimated thus far by in situ mapping experiments. The MAR derived from another gene, fushitarazu, also bound specifically to SP120. Immunostaining of whole cells and isolated nuclei with a monoclonal antibody raised against SP120 indicated that the protein is localized in a nuclear skeletal structure. These results suggest the involvement of SP120 in the MAR-mediated anchorage of nuclear DNA to the nuclear scaffold.
Insights
Researchers identified SP120, a protein that binds to matrix association regions (MAR), which are DNA segments crucial for anchoring nuclear DNA to the nuclear matrix. This finding suggests SP120
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Nuclear DNA associates with the nuclear matrix via specific DNA segments known as matrix association regions (MAR).
- Identifying proteins that interact with MAR is crucial for understanding DNA organization and nuclear structure.
Purpose of the Study:
- To identify and characterize proteins that recognize and bind to matrix association regions (MAR).
- To investigate the role of these MAR-binding proteins in the association of nuclear DNA with the nuclear matrix.
Main Methods:
- Used a plasmid containing an Ig kappa gene MAR for protein binding assays.
- Electrophoretic separation and membrane blotting to identify MAR-binding proteins.
- Protein purification, renaturation, and characterization of DNA-binding specificity.
- Immunostaining of cells and nuclei to determine protein localization.
Main Results:
- A 120,000 molecular weight protein, designated SP120, was identified as selectively binding to MAR.
- The MAR region, specifically a 365-bp fragment, was essential for SP120 binding, showing cooperative interaction.
- SP120 also bound to MAR from the fushitarazu gene, indicating broader MAR recognition.
- Immunostaining confirmed SP120's localization within the nuclear skeletal structure.
Conclusions:
- SP120 is a specific MAR-binding protein involved in the anchorage of nuclear DNA to the nuclear scaffold.
- The findings suggest SP120 plays a significant role in maintaining nuclear architecture through MAR-mediated DNA attachment.