 When an IRES segment is located between two reporter open reading frames in a eukaryotic mRNA molecule (a bicistronic mRNA), it can drive translation of the downstream protein coding region independently of the 5'-cap structure bound to the 5' end of the mRNA molecule.In such a setup, both proteins are produced in the cell.The first reporter protein located in the first cistron is synthesized by the cap-dependent initiation, while translation initiation of the second protein is directed by the IRES element located in the intercistronic spacer between the two reporter protein coding regions.