invention is the possibility to express two or more genes in multicistronic cassettes in yeast cells a further advantage of the present invention is the possibility to create viral vectors for expressing a foreign gene via adenine rich ireses in mammalian and especially in human cells another preferred embodiment of this invention is the creation of new iress on the basis of eukaryotic mrna 5 u2032 utr containing agnb s our analysis of 5 u2032 utrs of heat shock protein hsf mrnas revealed adenine rich 5 u2032 leaders moreover experimental testing of the nicotiana tabacum heat shock factor nthsf mrna leader confirmed this prediction nthsf 5 u2032 utr turned out to have ires activity not only in plant but also in human cells this invention provides 5 u2032 non translated regions of eukaryotic mrna that contain adenine rich sequences as ireses for the expression of several genes in multicistronic cassettes in plant or animal cells either transiently or via stable transformation transgenic organisms moreover such iress might be used for expression of foreign and natural genes in animal virus based vectors e g in gene therapy in the following the invention will be further described using specific examples standard molecular biological techniques were carried out according to sambrook et al 1989 molecular cloning a laboratory manual 2 nd edn cold spring harbor n y all plasmids utilized in.