Figure 7.

Model for the m½-sbsRNA-mediated SMD of mRNAs. mRNAs harboring a 3′ UTR B1, B2, and/or B4 SINE base-pair with a m½-sbsRNA via a partially complementary SINE of the same family to form a B1–B1, B2–B2, or B4–B4 SBS. At least for human SBSs, STAU1 and/or STAU2 can associate with the SBS and recruit UPF1 (Park et al. 2013). When translation terminates upstream of the SBS, SBS-bound mStau, which recruits mUpf1, triggers SMD of the mRNA. Data indicate that m½-sbsRNAs are not degraded, presumably because they are not translated.