Similar to our results and pointing to a crucial and conserved function of the RRMs, tethering of RRM14 of the yeast Pab1p also led to a robust inhibition of NMD, albeit weaker than full length Pab1p, whereas tethering of the C-terminal half of Pab1p barely stabilized the NMD reporter transcript. The finding that a fragment of Sup35p lacking the Pab1p interacting domain could suppress the slow growth phenotype of a sup35D strain and was able to stabilize the NMD reporter when tethered downstream of the PTC further implies that the PABP:eRF3 interaction is not essential for normal translation termination and for antagonizing NMD. Since the portion of PABPC1 that is necessary and sufficient for suppressing NMD encompasses the binding to eIF4G, we tested if the PABPC1:eIF4G interaction was critical for stabilization of the NMD reporter mRNA. Consistent with this idea, the M161A point mutation reduced PABPC1��s capacity to inhibit NMD. The fact that the RRM1-4 PABPC1 construct carrying the M161A mutation still co-precipitated to some extent with eIF4GI-MS2 indicates that this originally in vitro identified and tested point mutation is not sufficient to completely prevent binding to eIF4G in vivo. Further evidence for a critical role of the PABPC1:eIF4G interaction for the suppression of NMD was provided by PABPC1 tethering experiments in cells depleted for eIF4G, which resulted in Clofazimine diminished reporter mRNA levels. This hypothesis predicted that tethering of eIF4G should also suppress NMD. Consistent with this view, the full-length eIF4GI isoforms capable of interacting with PABPC1 increased the reporter transcript in tethering assays. A moderate increase was also induced by tethering the eIF4GIe constructs NT and VU 0364439 D682-1079, which both contain the binding sites for PABPC1 and for eIF4E and hence could potentially bring the end of the reporter mRNA close to the PTC. However, complicating the situation, these two eIF4GI variants had essentially the same effect on the construct B reporter mRNA, indicating that the observed reporter mRNA increase in this case did not require the complex to be close to the PTC.