The inclusion of PGRP-LC isoforms at the 3′ variable region is biased. (A) Exon–intron organization and multiple 3′ alternative cassettes of Drosophila PGRP-LC. Constitutive exons (black boxes), alternative exons (colored boxes), and introns (lines) are shown. The strength of the splice site is presented with the scores shown above. Splice site scores were calculated using a splice site prediction program (Reese et al. 1997) (range of 0–1). Three PGRP domains, a, x, and y, are alternatively spliced to the common exon 2 of the PGRP-LC gene. Letters denote the PGRP domains included in the alternative isoforms. The PGRP-LCy transcript is analogous to PGRP-LCx and uses the same 5′ splice site in exon 2, 57 bp upstream of the one used with the PGRP-LCa transcript (Werner et al. 2003). (B) 3D structural comparisons of PGRP splice isoforms. Green regions are encoded by alternative variants. (C) The alternative splicing pattern was analyzed by RT-PCR. The primers used in each experiment are depicted in A. (D) Heatmap of the expression of splice isoforms in different tissues. Based on the exon–exon junction reads from RNA-seq data, we calculated the splice isoforms in different tissues. These results indicate that PGRP-LC splice isoforms are biased toward x-S, y-S, and a-L in a tissue-specific manner.
