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Ca2+-binding proteins in nuclei
European Journal of Biochemistry
|December 1, 1980
Summary
Calcium ions (Ca2+) bind to proteins within cell nuclei, a process crucial for gene regulation. Nuclei from various animal tissues contain Ca2+-binding proteins that interact with chromatin, influencing gene expression.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Cell nuclei contain significant amounts of calcium (Ca2+), averaging 8-18 nmol Ca2+/mg protein across various species and tissues.
- Calcium ions are known to play roles in cellular signaling and regulation.
Purpose of the Study:
- To investigate the role of Ca2+-binding proteins within the cell nucleus.
- To determine the association of these proteins with chromatin and their potential role in gene regulation.
Main Methods:
- Nuclei were isolated from skeletal muscle (chick embryos, adult chickens, rabbits) and rat liver.
- Nuclei were digested with DNAase I and RNAase to degrade nucleic acids.
- Ca2+-binding proteins were identified and characterized using equilibrium dialysis and centrifuge transport assays.
Main Results:
- Nuclease digestion reduced Ca2+ binding by over 90%, indicating nucleic acids are major Ca2+ binders.
- Ca2+-binding proteins were identified in nonhistone chromosomal proteins and insoluble residues after nuclease treatment.
- These proteins interact with chromatin under specific ionic conditions (0.1 M KCl, 1 mM MgCl2).
Conclusions:
- Nonhistone chromosomal proteins and insoluble residues contain Ca2+-binding proteins.
- The interaction of these Ca2+-binding proteins with chromatin may be vital for regulating gene expression.
- This regulation is likely responsive to fluctuations in free Ca2+ concentrations within the cytoplasm and nucleoplasm.