Yeast nuclear RNA processing

Figure 8 Schematic representation of the three well-characterized functions of the TRAMP4/5 complex. A: Processing and degradation of NAB2 mRNA: the level of NAB2 mRNA is controlled by Nab2p, which recruits TRAMP and the exosome by binding to the A₂₆ site of the mRNA. Once TRAMP and the exosome are recruited the transcript is degraded; B: Degradation of un-modified/misfolded tRNA: tRNA that has not undergone modification at the correct time is preferentially polyadenylated by TRAMP. Once polyadenylated, the exosome aided by Mtr4p degrades the tRNA; C: ncRNA degradation: shown in panel C is the degradation of CUTs. The same pathway is followed for snRNA and snoRNA, which are processed and degraded by TRAMP and the exosome. Degradation of CUTs is performed co-transcriptionally as pictured. The levels of these RNAs cannot be detected without depletion of Rrp6p or Trf4p[92,111,112].