Complex sentence: This region of the viral genome is called internal ribosome entry site (IRES) which the first IRES to be discovered was found in the RNA of poliovirus, and it directs translation of the viral RNA.
Split into simpler sentences: This region of the viral genome is called internal ribosome entry site (IRES). The first IRES to be discovered was found in the RNA of poliovirus, and it directs translation of the viral RNA.