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Myeloperoxidase: a myeloid cell nuclear antigen with DNA-binding properties
1Division of Biological, Environmental, and Medical Research, Argonne National Laboratory, IL 60439-4833.
Summary
Myeloperoxidase (MPO) is found in human myeloid cell nuclei and protects DNA from oxygen radical damage. This enzyme plays a role in myeloid cell function and maturation.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Myeloperoxidase (MPO) is an enzyme present in myeloid cells.
- Its precise localization and function within these cells, particularly in the nucleus, require further investigation.
Purpose of the Study:
- To identify and characterize the antigen localized in myeloid cell nuclei.
- To investigate the interaction of myeloperoxidase (MPO) with DNA.
- To determine the potential role of nuclear MPO in protecting DNA from oxidative damage.
Main Methods:
- Murine monoclonal antibody H-43-5 was used to detect MPO in human myeloid cells.
- Immunoaffinity chromatography and CM-cellulose chromatography were employed for MPO purification.
- DNA-Sepharose chromatography and size-exclusion chromatography were used to study MPO-DNA interactions.
- Xanthine oxidase assay was performed to assess DNA protection from active oxygen species.
Main Results:
- The nuclear and cytoplasmic granule antigen was identified as myeloperoxidase (MPO).
- Nuclear MPO levels were highest in granulocytes, followed by HL-60 cells, monocytes, and monomyelocytic leukemia cells.
- Purified MPO from HL-60 cells fractionated into three forms (I, II, III), all binding tightly to DNA.
- MPO form III exhibited the highest affinity for DNA and could shield DNA from oxidative strand scission.
Conclusions:
- Intranuclear MPO is present in human myeloid cells, with varying levels across cell types.
- MPO binds to DNA, with different forms showing distinct affinities.
- Nuclear MPO may play a protective role in DNA integrity against oxygen radicals during myeloid cell processes.