Figure 2.

Model representing the post-transcriptional mechanisms regulating the CTH2 mRNA expression. CTH2 mRNA maturation starts with a 3′ extended transcript that is recognized by the Nrd1-Nab3 complex, and is subsequently processed by the nuclear exosome and the TRAMP4 polyadenylation complex. Eventually, the exosome pauses at a (GU_3–5)₅ site and Pap1 polyadenylates the trimmed CTH2 transcript. Moreover, CTH2 mRNA contains an ARE in its 3′ UTR which allows the binding of the Cth2 protein and auto-degradation. The auto-destabilization mechanism can be similar to other ARE-containing mRNAs and depends on the cytoplasmic 5′ to 3′ mRNA degradation machinery. Although not represented, Rat1 has also been implicated in the CTH2 transcript turnover.