GH1 splicing is regulated by multiple enhancers whose mutation produces a dominant-negative GH isoform that can be degraded by allele-specific small interfering RNA (siRNA).
The majority of mutations that cause isolated GH deficiency type II affect splicing of GH1 transcripts, leading to the production of a dominant-negative GH isoform. Because numerous mutations and polymorphisms throughout the GH1 gene have not yet been tested for aberrant splicing, we used a deletion mutagenesis screen across intron 2-exon 3-intron 3 to identify splicing regulatory sequences. These analyses identified a new enhancer element, ESE2, upstream of the cryptic splice site in exon 3 and further defined a previously described enhancer (ESE1) to include the first seven nucleotides of exon 3. Besides enhancers, the overall size of intron 3 is also crucial for exon inclusion. Given the deleterious effects of the dominant-negative 17.5-kDa isoform, these and previous studies underscore the extent to which splicing regulatory elements serve to prevent exon skipping. Importantly, we show here that small interfering RNAs can be used to specifically degrade exon 3-skipped transcripts, potentially a new avenue of therapeutic intervention in isolated GH deficiency II and other dominant disorders.
Box 1820 Station B, Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA.
Robin C C
RC
Ryther
Alex S
AS
Flynt
Bryan D
BD
Harris
John A
JA
Phillips
James G
JG
Patton
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004274:DNA, Recombinant; D004742:Enhancer Elements, Genetic / Q000235:genetics / Q000502:physiology*; D005091:Exons; D017353:Gene Deletion; D005799:Genes, Dominant; D019382:Human Growth Hormone / Q000235:genetics*; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D020033:Protein Isoforms / Q000235:genetics; D034741:RNA, Small Interfering / Q000502:physiology*
D004274:DNA, Recombinant; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D019382:Human Growth Hormone