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Exon-skipping in BCR/ABL is induced by ABL exon 2
1Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada.
The Biochemical Journal
|May 5, 2000
Summary
Alternative splicing in chronic myelogenous leukaemia (CML) involves BCR/ABL transcripts. A specific element in ABL exon 2 drives this exon skipping in CML cells, mimicking patient splicing patterns.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- The BCR/ABL fusion gene is a hallmark of chronic myelogenous leukaemia (CML).
- Alternative splicing of BCR/ABL, producing p190 and p210 transcripts, occurs in approximately 60% of CML patients.
- This alternative splicing involves exon skipping, where ABL exon 2 joins variable upstream BCR exons.
Purpose of the Study:
- To investigate the molecular mechanisms underlying BCR/ABL alternative splicing.
- To identify the specific sequences responsible for exon-skipping events in BCR/ABL.
- To develop a model explaining the role of ABL exon 2 in this splicing phenomenon.
Main Methods:
- Construction and transfection of BCR and BCR/ABL minigenes into various cell types.
- Assessment of alternative splicing using reverse transcriptase PCR (RT-PCR).
- Localization of the critical sequence element within ABL exon 2.
Main Results:
- BCR minigenes alone did not exhibit exon skipping.
- Insertion of genomic DNA containing ABL exon 2 induced exon skipping, but only in CML cell lines (K562, EM3).
- The sequence element responsible for promoting exon skipping was localized to ABL exon 2 itself.
Conclusions:
- ABL exon 2 contains a critical element that mediates alternative splicing and exon skipping in BCR/ABL.
- This finding replicates the splicing phenotype observed in most CML patients.
- A model is proposed involving a trans-acting factor in CML cells interacting with ABL exon 2 pre-mRNA to promote upstream BCR exon skipping.