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Multiple forms of nuclear deoxyribonuclease in rat thymocytes
1Department of Biochemistry, Faculty of Pharmaceutical Sciences, Science University of Tokyo, Japan.
Biochemical and Biophysical Research Communications
|September 15, 1994
Summary
DNase gamma, a neutral endonuclease, plays a key role in DNA fragmentation during apoptosis in rat thymocytes. Its activity is retained in apoptotic cells, unlike DNases alpha and beta.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Apoptosis involves DNA fragmentation, a process mediated by endonucleases.
- Specific endonucleases in rat thymocytes have been investigated for their roles in DNA degradation.
Purpose of the Study:
- To isolate and characterize distinct endonucleases from rat thymocyte nuclei.
- To determine the specific role of these endonucleases in DNA fragmentation during apoptosis.
Main Methods:
- Isolation and purification of three distinct endonucleases (DNase alpha, beta, and gamma) from rat thymocyte nuclei.
- Chromatographic analysis and molecular mass determination of the isolated DNases.
- Assay of DNase activity in the presence of various divalent cations (Ca2+, Mg2+, Zn2+).
- Analysis of DNase activity in apoptotic rat thymocyte nuclei induced by gamma-ray irradiation or glucocorticoid.
Main Results:
- Three endonucleases, DNase alpha, beta, and gamma, were isolated with distinct properties.
- DNase gamma is a neutral endonuclease requiring Ca2+ and Mg2+, while DNases alpha and beta are acidic and cation-independent.
- All three DNases degraded chromatin to nucleosomal fragments.
- DNase gamma activity was retained in apoptotic thymocyte nuclei, whereas DNase alpha and beta activities were reduced.
Conclusions:
- DNase gamma is the primary endonuclease responsible for DNA fragmentation during apoptosis in rat thymocytes.
- The differential activity of DNases alpha, beta, and gamma provides insights into the regulation of DNA degradation in apoptosis.