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Characterization of functional messenger RNA splice variants of BRCA1 expressed in nonmalignant and tumor-derived
1Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Abstract:
BRCA1 has been identified as a tumor suppressor gene that is mutated in many cases of inherited breast and ovarian cancer. Recent data suggest that multiple splice forms of BRCA1 exist, but the structure and function of these alternative transcripts have not been elucidated. By sequence analysis of reverse transcription-PCR products, we have determined that a major splice form of BRCA1 expressed in malignant and nonmalignant breast epithelial cells contains an in-frame deletion of 3309 nucleotides from exon 11. A second alternative splice event results in the in-frame deletion of the 123 nucleotides that make up exons 9 and 10. These splice variants are found on polysomes and are therefore predicted to encode 80-85-kDa BRCA1-derived proteins lacking approximately 60% of the internal amino acids that constitute full-length BRCA1.
Insights
Researchers discovered new BRCA1 splice variants in breast cells. These variants lack significant portions of the gene, potentially impacting tumor suppressor functions in breast and ovarian cancers.
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- BRCA1 is a critical tumor suppressor gene frequently mutated in hereditary breast and ovarian cancers.
- Evidence suggests the existence of multiple BRCA1 splice forms, but their structures and functions remain largely unknown.
Purpose of the Study:
- To investigate the structure and function of alternative BRCA1 transcripts.
- To identify and characterize novel BRCA1 splice variants in breast epithelial cells.
Main Methods:
- Sequence analysis of reverse transcription-polymerase chain reaction (RT-PCR) products.
- Analysis of splice variants in malignant and nonmalignant breast epithelial cells.
Main Results:
- A major BRCA1 splice form with a 3309-nucleotide in-frame deletion from exon 11 was identified.
- A second splice variant featuring an in-frame deletion of exons 9 and 10 (123 nucleotides) was also found.
- These variants were detected on polysomes, indicating they are translated into proteins.
Conclusions:
- Alternative splicing generates truncated BRCA1 proteins (80-85 kDa) lacking approximately 60% of internal amino acids.
- These findings reveal novel BRCA1 splice variants with potential implications for breast and ovarian cancer development and progression.