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Structure and promoter analysis of murine CAD and ICAD genes
K Kawane1, H Fukuyama, M Adachi
1Department of Genetics, Osaka University Medical School, Osaka, Japan.
Abstract:
Caspase-activated DNase (CAD) degrades chromosomal DNA during apoptosis, whereas ICAD (inhibitor of CAD) inhibits the CAD's DNase by binding to it. Here, we describe the assignment of murine CAD and ICAD genes to the distal part of murine chromosome 4. Molecular cloning and structural analysis indicated that CAD and ICAD genes are comprised of 7 and 6 exons, respectively. Two different ICAD mRNAs coding for two forms of ICAD proteins (ICAD-S and ICAD-L) were found to be produced by alternative splicing of intron 5. The CAD and ICAD mRNAs were detected ubiquitously in various murine tissues. Analyses of the promoter activity with a series of deletion mutants of their 5' flanking regions indicated that a 190-bp 5' flanking region of the CAD gene was sufficient to promote the transcription. Whereas, a 120-bp flanking region of ICAD gene was required to promote its transcription. These regions do not show similarity between CAD and ICAD genes, suggesting that expression of CAD and ICAD genes is regulated by different mechanisms.
Insights
Researchers mapped the murine Caspase-activated DNase (CAD) and inhibitor of CAD (ICAD) genes to chromosome 4. They found alternative splicing produces two ICAD forms, with distinct promoter regions suggesting different gene regulation mechanisms.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Caspase-activated DNase (CAD) degrades DNA during apoptosis.
- Inhibitor of CAD (ICAD) binds and inhibits CAD activity.
- Understanding CAD/ICAD gene regulation is crucial for apoptosis research.
Purpose of the Study:
- To map the murine CAD and ICAD genes.
- To analyze the structural organization and expression of CAD and ICAD.
- To investigate the transcriptional regulation of CAD and ICAD.
Main Methods:
- Gene mapping using murine chromosome analysis.
- Molecular cloning and structural analysis of CAD and ICAD genes.
- Analysis of gene expression in various murine tissues.
- Reporter assays to determine promoter activity using deletion mutants.
Main Results:
- Murine CAD and ICAD genes assigned to distal chromosome 4.
- CAD gene has 7 exons, ICAD gene has 6 exons.
- Alternative splicing of ICAD intron 5 generates ICAD-S and ICAD-L isoforms.
- CAD and ICAD mRNAs are ubiquitously expressed.
- A 190-bp 5' flanking region of CAD and a 120-bp region of ICAD are sufficient for transcription.
- CAD and ICAD promoter regions show no sequence similarity.
Conclusions:
- The murine CAD and ICAD genes are located on chromosome 4.
- Alternative splicing contributes to ICAD functional diversity.
- CAD and ICAD gene expression is regulated by distinct promoter mechanisms.