Dna Ligase Iv Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| Protein Name | DNA Ligase IV |
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| Gene Symbol | LIG4 |
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| UniProt ID | P18858 |
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| Molecular Weight | ~100 kDa |
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| Subcellular Localization | Nucleus |
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| Protein Family | DNA ligase family |
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## Overview
This section provides a comprehensive overview of the gene/protein and its role in the nervous system and neurodegenerative diseases.
DNA Ligase IV is a 911-amino acid protein with a unique architecture:
- N-terminal catalytic domain (residues 1-300): Contains the adenylation domain typical of DNA ligases
- BRCT domain (C-terminal, residues 750-911): Protein-protein interactions with XRCC4
- Interdomain linker (residues 300-400): Flexible region
Forms a stable 1:1 complex with XRCC4 through the BRCT domain interactions.
DNA Ligase IV is the ligase specifically required for the final step of classical NHEJ:
Ligation Reaction:
- ATP + ligase → AMP + ligase-AMP (adenylation)
- Ligase-AMP transfers AMP to 5'-phosphate of DNA
- Nucleophilic attack by 3'-OH forms phosphodiester bond
- AMP released, ligase recycled
Biological Functions:
- Essential for V(D)J recombination in developing B and T cells
- Critical for repair of ionizing radiation-induced DSBs
- Maintains genomic stability in all proliferating cells
In neurons, LIG4-mediated repair is important for maintaining genomic integrity despite the lack of replication.
LIG4 Syndrome:
- Rare autosomal recessive disorder
- Features: microcephaly, growth retardation, immunodeficiency, pancytopenia
- Predisposition to malignancies
- Cellular phenotype: radiosensitivity, defective V(D)J recombination
Cancer:
- LIG4 polymorphisms associated with cancer risk
- Somatic mutations found in some tumors
Therapeutic approaches:
- Gene therapy: Potential for LIG4-deficient patients
- Radiosensitizers: Inhibition to enhance cancer therapy
- Synthetic lethality: PARP inhibitors show synthetic lethality with NHEJ defects
Clinical applications limited by the essential nature of NHEJ.
- Ramsden & Gellert, XRCC4 and ligase IV complete NHEJ (1998)
- O'Driscoll et al., LIG4 syndrome (2001)
LIG4 Gene, Non-Homologous End Joining, XRCC4 Protein, DNA Repair
The study of Dna Ligase Iv Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
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