STAT3 alternative spicing
A highly conserved exon 21 of the human STAT3 gene served as a model to study splicing mechanisms in tandem donor splice site (5'ss). The study aimed to characterize determinants of tandem splice site choice. A specialized minigene containing exon 21 was used for high-throughput splicing analysis. This minigene was extensively mutated in 5'ss covering positions -7 to +8 (library L1) and positions +9 to +19 (library L2) to create a range of 5'ss variants. These variants' splicing pattern is characterised in dependence on the presence of endogenous U1 snRNA only, or artificial shifted U1 snRNAs binding out of authentic 5'ss.