Fig. 1.

Nine-nucleotide IRES module functions as a translational enhancer in a monocistronic context. A schematic representation of the Photinus luciferase monocistronic constructs is indicated. The 5′ leader sequences include five linked copies of the Gtx 9-nt IRES module, indicated as gray bars, and a control (SI/SIII) in which the Gtx sequences have been mutated to poly(A), indicated by thin black lines. Both constructs contain 25 nt of the mouse β-globin 5′ UTR sequence upstream of the Photinus luciferase initiation codon. These 25 nucleotides are represented by a thick black line. Constructs were assayed in transiently transfected N2a cells. Translation efficiencies were determined per unit mRNA and normalized to 1.0 for those obtained with the control construct containing the SI/SIII sequence. Horizontal lines indicate SEM.