Position-dependent alternative splicing activity revealed by global profiling of alternative splicing events regulated by PTB (Exon array). Homo sapiens

To gain global insights into the role of the well-known repressive splicing regulator PTB we analyzed the consequences of PTB knockdown in HeLa cells using high-density oliogonucleotide splice-sensitive microarrays. The major class of identified PTB-regulated splicing event was PTB-repressed cassette exons, but there was also a substantial number of PTB-activated splicing events. PTB repressed and activated exons showed a distinct arrangement of motifs with pyrimidine-rich motif enrichment within and upstream of repressed exons, but downstream of activated exons. The N-terminal half of PTB was sufficient to activate splicing when recruited downstream of a PTB-activated exon. Moreover, insertion of an upstream pyrimidine tract was sufficient to convert a PTBactivated to a PTB-repressed exon. Our results demonstrate that PTB, an archetypal splicing repressor, has variable splicing activity that predictably depends upon its binding location with respect to target exons. Overall design: Target was prepared from 6 biological replicates of PTB/nPTB knockdown and 6 control mock knockdowns from HeLa S3 cell line and hybridized to the Affymetrix Human Exon 1.0 ST Array. Two groups of three replicates each were collected at two different times.