...neither cast ye your pearls before swine...

Another one incredibly stupid experiment from M.Holcik's lab. We have ravished one of their papers already. Now let's look at a new one:

Liwak, U. et al. Tumour Suppressor PDCD4 Represses IRES-Mediated Translation of Anti-Apoptotic Proteins and is Regulated by S6 Kinase 2. Mol Cell Biol (2012).doi:10.1128/MCB.06317-11

What authors claim is that PDCD4 specifically binds to XIAP mRNA 5'UTR and inhibits translation of the latter. Apart from in vivo data, which could seem to be consistent (and will be discussed elsewhere), there are some in vitro experiments presented. Bad luck.

The intention of the very last figure was to demonstrate that PDCD4 inhibits XIAP translation in RRL. So they added PDCD4 to RRL and 

observed that the ability of the XIAP IRES to recruit ribosomes (as determined by a toeprint +17 to +19 nt downstream of AUG) was severely impaired in the presence of His-PDCD4 (Fig. 5B, compare lanes 1, 2 and 4, 5). In contrast, addition of GST had no impact on the formation of the XIAP 48S complex (lanes 3, and 4, 5).

1.  PDCD4 is a homolog of eIF4G. It possesses a binding site for translational RNA helicase eIF4A, but contrary to eIF4G, which enhances helicase activity, PDCD4 inhibits one (1). Conformably, it inhibits cap-dependent and EMCV IRES-dependent translation, the both being eIF4A-dependent. And -  surprise! - PDCD4 must inhibit XIAP translation, since it is also eIF4A-dependent. So this experiment lacks control: any other eIF4A-dependent mRNA. Otherwise, one can add dominant-negative eIF4A mutant (R362Q, for example) to XIAP mRNA and claim that eIF4A is specifically required for XIAP translation. That's stupid.

2. Again, the authors don't give a fuck to differences of intensities of the full-length bands in RT assay (see comment here).

That's ridiculous.

1. Yang, H.-S. et al. The transformation suppressor Pdcd4 is a novel eukaryotic translation initiation factor 4A binding protein that inhibits translation. Mol Cell Biol 23, 26–37 (2003).