Figure 7.

mRNA decay activation by the TTP family of ARE-binding proteins. (A) Three steps of mRNA decay. Activation of mRNA decay is poorly understood, indicated by a question mark. Regulation of mRNA decay is hypothesized to take place on the recognition or activation steps. mRNA decay enzymes are shown as “Pac-men.” (B) How TTP may activate ARE-mediated decay by recruitment of trans-acting factors, which includes mRNA decay enzymes via the NTD. The putative activation of 5′-to-3′ exonucleolytic decay is shown in brackets because it is based solely on the interaction between hXrn1 and TTP/BRF-1 shown in this study. All other indicated decay processes are based on both interaction and decay data. For details, see Discussion. The NTD is shown facing the poly-A tail based on the solution structure of the BRF-2 zinc-finger complexed with RNA (Hudson et al. 2004).