Based on the results, our mechanistic hypothesis for the Sbp1-specific translation regulation is the following (Fig. 7): The two RRM domains of Sbp1 bind to 5′UTRs cooperatively, and the center RGG domain recruits other proteins. These interactions lead to formation of an RNP assembly on the UTR, which modulates the translation of targeted mRNAs. In the case of 5′UTRPab1, the RGG domain interacts with other proteins including Pab1, and the resulting RNP complex inhibits the translation initiation of Pab1 mRNA. Because Pab1 is a general translation factor, the observed down-regulation of this protein by Sbp1 may explain at least in part why Sbp1 inhibits the global translation of mRNAs in the cell.