Figure 1

Overview of representative PDE4 gene structure. PDE4 genes are composed of multiple exons connected by either a dashed line (facultative exons), or solid line (constitutive exons). The PDE4 long form amino-termini specifying exons (1), are located in the upstream region of the genes, each under different promoter control. The Upstream conserved region-1 (UCR1) is composed of three exons (UCR1a, UCR1b, and UCR1c). The PDE4 short form amino termini specifying exon(s) (1a) are located downstream of the linker region 1 (LR1) exon. Upstream conserved region 2 (UCR2) is composed of three exons (UCR2a, UCR2b and UCR2c), which are interrupted by the super-short form amino-terminus specifying exon (1b). The amino-terminus of truncated super-short PDE4 splice variants is found within the UCR2b exon (1c). The enzymatic core of PDE4 is encoded by several constitutive exons (found in all isoforms) located in the farthest downstream regions of the gene.