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Reverse replication timing for the XIST gene in human fibroblasts
R S Hansen1, T K Canfield, S M Gartler
1Department of Medicine, University of Washington, Seattle 98195, USA.
Human Molecular Genetics
|May 1, 1995
Summary
The XIST gene
Area of Science:
- Epigenetics
- Molecular Biology
- Genetics
Background:
- Gene expression is regulated by DNA replication timing.
- Active genes replicate earlier than inactive genes.
- X chromosome inactivation involves differential gene replication.
Purpose of the Study:
- Investigate the replication timing of the XIST gene.
- Determine if XIST follows established gene replication patterns.
- Explore exceptions to replication timing regulation.
Main Methods:
- Cell culture of human fibroblasts.
- Analysis of DNA replication timing.
- Comparison of expressed and silenced XIST alleles.
Main Results:
- The expressed XIST allele replicates late, while the silent allele replicates early.
- This pattern is an exception to the typical gene replication timing.
- Findings contrast with previous in situ hybridization studies.
Conclusions:
- The 'reverse' replication timing of XIST may be functionally significant.
- Allele-specific structural differences could explain replication timing.
- This challenges established models of epigenetic regulation.