Dual luciferase and mRNA stability plasmids have been previously described (15) . Oligonucleotide primers were purchased from Integrated DNA Technologies (Coralville, IA, USA) and are shown in Supplementary  Table S2 . Computationally identified putative À1 RF signals were amplified from yeast genomic DNA using PCR using Oligonucleotide primers which terminated in a SalI restriction site at the 5 0 and BamHI at the 3 0 . The zero-frame dual-luciferase reporter plasmid (pJD375) along with the -1 RF signal containing dsDNA fragments were digested using these restriction enzymes and ligated together to generate endogenous -1 RF signal containing dual-luciferase vectors. Oligonucleotide primers were chosen to terminate in KpnI restriction sites and amplify 41 and 30 bases of Renilla and firefly luciferase derived sequences respectively. The resulting amplicons were cloned into the KpnI site 492 bases into the PGK1 open reading frame of the unmodified PGK1 containing vector (pJD741). A premature termination codon vector (pJD828) was generated by cutting the readthrough (pJD753) with BamHI and backfilling with Klenow fragment. Plasmids so generated are described in Supplementary Table S3 .