FIGURE 5.

Model for rapid degradation of truncated aberrant protein derived from aberrant mRNA containing a specific premature termination codon. a, premature translation termination leads to recruitment of Upf1. b, when truncated polypeptide is unfolded, Upf complex forms a complex with truncated polypeptide. c, the PTC product is released from ribosome but still associates with Upf complex. d, finally, Upf complex-truncated polypeptide complex is rapidly degraded by the proteasome in a ubiquitination-independent manner.