IRES activity of m<i>Per1</i> 5′UTRs.

<p>(A) Schematic diagram of bicistronic reporter plasmids. 5′UTRs were inserted into intergenic region between Rluc and Fluc. Bicistronic reporter plasmid (pRF), <i>Renilla</i> luciferase (Rluc), and <i>firefly</i> luciferase (Fluc). (B) NIH 3T3 cells were transiently transfected with bicistronic reporters that harbor 5′UTRs of <i>Per1</i>, <i>Bip</i>, and <i>c-Myc</i>. After 24 h incubation, cells were subjected to luciferase assay. The results are expressed as the mean ± SEM. (C) Bicistronic reporters that harbor 5′UTRs were transfected to HEK 293A cells. After 24 h, cells were harvested, and total RNAs were prepared and subjected to Northern blotting. Total RNA (2.5 µg) was hybridized with a specific probe for the <i>Fluc</i> coding region. 18S and 28S RNAs are shown as controls. The data was quantified by measuring the ratio of Fluc/28S.