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Regulation of Ich-1 pre-mRNA alternative splicing and apoptosis by mammalian splicing factors
1Department of Pediatrics and Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Abstract:
The importance of alternative splicing in regulating apoptosis has been suggested by findings of functionally antagonistic proteins generated by alternative splicing of several genes involved in apoptosis. Among these, Ich-1 (also named as caspase-2) encodes a member of the caspase family of proteases. Two forms of Ich-1 are produced as a result of alternative splicing: Ich-1L, which causes apoptosis, and Ich-1S, which prevents apoptosis. The precise nature of Ich-1 alternative splicing and its regulation remain unknown. Here, we show that the production of Ich-1L and Ich-1S transcripts results from alternative exclusion or inclusion of a 61-bp exon. Several splicing factors can regulate Ich-1 splicing. Serine-arginine-rich proteins SC35 and ASF/SF2 promote exon skipping, decreasing the ratio of Ich-1S to Ich-1L transcripts; whereas heterogeneous nuclear ribonucleoprotein A1 facilitates exon inclusion, increasing this ratio. Furthermore, in cultured cells, SC35 overexpression increases apoptosis; whereas heterogeneous nuclear ribonucleoprotein A1 overexpression decreases apoptosis. These results provide the first direct evidence that splicing factors can regulate Ich-1 alternative splicing and suggest that alternative splicing may be an important regulatory mechanism for apoptosis.
Insights
Alternative splicing of Ich-1 (caspase-2) generates forms that regulate apoptosis. Splicing factors like SC35 and hnRNP A1 control this process, impacting cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Alternative splicing generates functionally antagonistic proteins involved in apoptosis.
- Ich-1 (caspase-2) produces two forms, Ich-1L (apoptosis-inducing) and Ich-1S (apoptosis-inhibiting), via alternative splicing.
- The regulation of Ich-1 alternative splicing remains unclear.
Purpose of the Study:
- To elucidate the mechanism of Ich-1 alternative splicing.
- To identify splicing factors that regulate Ich-1 alternative splicing.
- To investigate the functional consequences of altered Ich-1 splicing on apoptosis.
Main Methods:
- Analysis of Ich-1 transcript variants.
- Investigating the role of a specific 61-bp exon in Ich-1 splicing.
- Assessing the impact of splicing factors (SC35, ASF/SF2, hnRNP A1) on Ich-1 splicing ratios.
- Overexpression studies in cultured cells to link splicing factor activity to apoptosis.
Main Results:
- Ich-1L and Ich-1S production results from alternative inclusion or exclusion of a 61-bp exon.
- SC35 and ASF/SF2 promote exon skipping, reducing the Ich-1S/Ich-1L ratio.
- hnRNP A1 facilitates exon inclusion, increasing the Ich-1S/Ich-1L ratio.
- SC35 overexpression enhances apoptosis, while hnRNP A1 overexpression inhibits it.
Conclusions:
- Splicing factors directly regulate Ich-1 alternative splicing.
- Alternative splicing of Ich-1 is a key regulatory mechanism controlling apoptosis.
- This study provides direct evidence linking splicing factor activity to apoptosis regulation.