“…The most common test involves transposing a suspected IRES from its normal 5′ position to the midpoint of a synthetic dicistronic transcript and asking whether this allows translation of the 3′ cistron. The test is undermined in many cases, however, because the candidate IRES turns out to harbor a cryptic promoter or splice site, causing the dicistronic DNA vector to produce an unintended monocistronic mRNA (Dumas et al, 2003;Han and Zhang, 2002;Han et al, 2003a,b;Hecht et al, 2002;Liu et al, 2005;Sherrill et al, 2004;Van Eden et al, 2004;Vergé et al, 2004;Wang et al, 2005b). In many other cases, the RNA analyses required to rule out a cryptic promoter or splice site simply were not done.…”