title: Evolutionary constraint helps unmask a splicing regulatory region in BRCA1 exon 11.
abstract: BACKGROUND
  Alternative splicing across exon 11 produces several BRCA1 isoforms. Their proportion varies during the cell cycle, between tissues and in cancer suggesting functional importance of BRCA1 splicing regulation around this exon. Although the regulatory elements driving exon 11 splicing have never been identified, a selective constraint against synonymous substitutions (silent nucleotide variations that do not alter the amino acid residue sequence) in a critical region of BRCA1 exon 11 has been reported to be associated with the necessity to maintain regulatory sequences.
  
  
  RESULTS
  Here we have designed a specific minigene to investigate the possibility that this bias in synonymous codon usage reflects the need to preserve the BRCA1 alternative splicing program. We report that in-frame deletions and translationally silent nucleotide substitutions in the critical region affect splicing regulation of BRCA1 exon 11.
  
  
  CONCLUSIONS
  Using a hybrid minigene approach, we have experimentally validated the hypothesis that the need to maintain correct alternative splicing is a selective pressure against translationally silent sequence variations in the critical region of BRCA1 exon 11. Identification of the trans-acting factors involved in regulating exon 11 alternative splicing will be important in understanding BRCA1-associated tumorigenesis.
authors.affiliation: Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.
authors.forename: Michela
authors.initials: M
authors.lastname: Raponi
authors.forename: Andrew G L
authors.initials: AG
authors.lastname: Douglas
authors.forename: Claudia
authors.initials: C
authors.lastname: Tammaro
authors.forename: David I
authors.initials: DI
authors.lastname: Wilson
authors.forename: Diana
authors.initials: D
authors.lastname: Baralle
mesh_terms: D017398:Alternative Splicing; D005075:Biological Evolution; D001943:Breast Neoplasms / Q000235:genetics; D045744:Cell Line, Tumor; D003062:Codon; D005091:Exons; D005260:Female; D017353:Gene Deletion; D019398:Genes, BRCA1 / Q000502:physiology*; D006801:Humans; D009154:Mutation; D012045:Regulatory Sequences, Nucleic Acid; D015534:Trans-Activators / Q000235:genetics
chemical_list: D003062:Codon; D015534:Trans-Activators