Figure 1.

Structure of ribosomal protein S8 gene and evidence for trans-splicing. (A) Alignment of selected ESTs from three distinct variants of RP S8 with the genomic sequences of the Variant 2 of RP S8 (arrow, "gene"). Transcripts from each variant clearly show alternatively the TAC (red) and TTT (blue) motifs, which are absent from the corresponding genomic region. (B) The characterization of several PCR products and their comparison with EST sequences allowed us to determine the positions and lengths of the introns as well as those of the 5' UTR, the coding sequence (CDS) and the upstream region. The post-transcriptional addition of splice-leaders (SL) is schematized: the two alternative classes of SLs (TAC and TTT) have been retrieved in the RP S8 transcripts present in the library. Alignment corresponding to this schematic representation is available as Additional file 6. (C) The splice-leader genes encoding the two forms of splice-leaders are located in the 5S cluster region. Each splice-leader gene includes the splice-leader sequence and the outron, which is excised during the trans-splicing processing. Alignment corresponding to this schematic representation is available as Additional file 7.