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A CD45 polymorphism associated with multiple sclerosis disrupts an exonic splicing silencer
1Departments of Medicine and of Microbiology and Immunology and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California 94143-0795, USA.
The Journal of Biological Chemistry
|April 18, 2001
Summary
A genetic variation linked to multiple sclerosis enhances CD45 protein splicing. This study reveals how a specific silencer element (ESS1) disruption by the polymorphism alters CD45 exon 4 splicing, impacting immune function.
Area of Science:
- Molecular Biology
- Immunology
- Genetics
Background:
- CD45 protein-tyrosine phosphatase plays a crucial role in immune system regulation.
- A specific single nucleotide polymorphism in CD45 is associated with increased susceptibility to multiple sclerosis.
- Altered splicing of CD45 exon 4 has been observed in relation to this polymorphism.
Purpose of the Study:
- To elucidate the molecular mechanism by which a CD45 polymorphism enhances exon 4 splicing.
- To identify and characterize splicing regulatory elements within CD45 exon 4.
- To understand how these elements influence CD45 splicing and its link to multiple sclerosis.
Main Methods:
- Analysis of splicing regulatory elements within CD45 exon 4.
- Functional characterization of an exonic splicing silencer (ESS1).
- Investigation of ESS1 interaction with nuclear extracts and its effect on splice sites.
Main Results:
- At least four splicing regulatory elements were identified in CD45 exon 4.
- The strongest element, ESS1, acts as an exonic splicing silencer for the weak 5' splice site.
- Disruption of ESS1 by the polymorphism leads to enhanced splicing of CD45 exon 4.
- ESS1 also represses heterologous splice sites and interacts with nuclear complexes.
Conclusions:
- The CD45 polymorphism enhances exon 4 splicing by disrupting the ESS1 silencer.
- A delicate balance between splicing enhancers and silencers (like ESS1) regulates CD45 exon 4 splicing.
- Proper immune system function relies on the precise regulation of CD45 splicing.