Figure 7.

A model to illustrate how formation of a nuclear mRNP containing the PTB complex could be required for cellular IRES activity. Our data suggest remodelling of a PTB-containing complex occurs following treatment with the apoptosis-inducing ligand TRAIL. Thus, the IRES-inhibitory protein hnRNPA1 decreases in association with PTB, whereas the IRES-stimulatory proteins NONO/p54^nrb, PSF and hnRNPA2/B1 increase in association. This complex then binds to the IRES RNA, and shuttles to the cytoplasm as an mRNP. Here, further IRES-stimulatory proteins including DDX3X and YBX1 are recruited to the complex, which is then competent to stimulate apoptotic IRES-mediated translation