Genomic organization of HPSE gene. Numbered boxes represent the 14 exons. Gray boxes represent the ORF and white boxes represent the 5′ and 3′ untranslated regions. The black region represents the sequence of intron that form part of HPSE 1b. The location of PCR primers is indicated by arrows. (A) 5′ end of isoforms HPSE1a and HPSE 1b. (B) Location of the 185-bp sequence within the 3′ unstranslated region that mediates HPSE down-regulation.