FIG. 4.

The poly(A) tail is required for CIRE-1 and CIRE-2 regulatory function. The regulatory function and 5′-end dependence of the full-length TEV 5′ leader and each CIRE individually were examined by introducing each sequence upstream of the luc coding region. Each uncapped mRNA, with or without an SL present at the 5′ terminus, was synthesized in vitro without a poly(A) tail. The region of the TEV 5′ leader present in each construct is indicated by a thick line, and the portion of the TEV leader sequence included in each construct is indicated as a subscript. The 24-bp SL introduced into each construct is indicated diagrammatically. Control sequence is indicated by a thin line, and the length of the control sequence (Con) included in the control construct is indicated as a subscript. Expression from each mRNA following delivery to carrot protoplasts by electroporation is shown to the right of each construct.