Tannic acid facilitates expression of the polypyrimidine tract binding protein and alleviates deleterious inclusion of CHRNA1 exon P3A due to an hnRNP H-disrupting mutation in congenital myasthenic syndrome.
We recently reported that the intronic splice-site mutation IVS3-8G>A of CHRNA1 that encodes the muscle nicotinic acetylcholine receptor alpha subunit disrupts binding of a splicing repressor, hnRNP H. This, in turn, results in exclusive inclusion of the downstream exon P3A. The P3A(+) transcript encodes a non-functional alpha subunit that comprises 50% of the transcripts in normal human skeletal muscle, but its functional significance remains undetermined. In an effort to search for a potential therapy, we screened off-label effects of 960 bioactive chemical compounds and found that tannic acid ameliorates the aberrant splicing due to IVS3-8G>A but without altering the expression of hnRNP H. Therefore, we searched for another splicing trans-factor. We found that the polypyrimidine tract binding protein (PTB) binds close to the 3' end of CHRNA1 intron 3, that PTB induces skipping of exon P3A and that tannic acid increases the expression of PTB in a dose-dependent manner. Deletion assays of the PTB promoter region revealed that the tannic acid-responsive element is between positions -232 and -74 from the translation initiation site. These observations open the door to the discovery of novel therapies based on PTB overexpression and to detecting possible untoward effects of the overexpression.
Bian
Yang
Y
Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Masuda
Akio
A
Matsuura
Tohru
T
Ito
Mikako
M
Okushin
Kazuya
K
Engel
Andrew G
AG
Ohno
Kinji
K
D001483:Base Sequence; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005091:Exons / Q000235:genetics*; D034541:Heterogeneous-Nuclear Ribonucleoprotein Group F-H / Q000235:genetics*; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007438:Introns / Q000235:genetics; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D020294:Myasthenic Syndromes, Congenital / Q000235:genetics*; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D022821:RNA Splice Sites / Q000235:genetics; D012326:RNA Splicing / Q000187:drug effects; D011978:Receptors, Nicotinic / Q000235:genetics*; D017384:Sequence Deletion; D013634:Tannins / Q000494:pharmacology*
C523021:CHRNA1 protein, human; D034541:Heterogeneous-Nuclear Ribonucleoprotein Group F-H; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C450006:PTBP1 protein, human; D022821:RNA Splice Sites; D011978:Receptors, Nicotinic; D013634:Tannins; D038941:Polypyrimidine Tract-Binding Protein; D008156:Luciferases