Test system for determination of HIV-1 frameshifting efficiency in animal cells.

We have developed a system in animal cells which allows the quantification of frameshifting determined by specific mRNA sequences. The method is based on the expression of an N-terminally extended firefly luciferase gene which requires frameshifting in order to be translated as a functional enzyme. The systems sensitivity is such that it allows the detection of even low efficiency of frameshifting. Our results show that the HIV-1 frameshift sequence including the 3' located stem-loop structure leads to ribosomal frameshifting at a lower level than that described for in vitro systems when tested in several fibroblastoid cell lines.