Review Article

Polyuridylation in Eukaryotes: A 3′-End Modification Regulating RNA Life

Figure 3

Known functions of polyuridylation in the cytoplasm. (a) In S. pombe, polyuridylation of mRNAs by Cid1 PUP leads to decapping and decay. (b) In Humans, histone mRNAs are uridylated by ZCCHC11 followed by LSM1-7 complex binding. ERI1 enzyme will then bind the LSM1-7 complex inducing the histone mRNA stem loop. The stem loop degradation will stall and reoligouridylation and possibly UPF1 helicase activity are needed in order to proceed. The remains of the stem loop are degraded leading to histone mRNA decay from the 5′ and/or 3′-end. The exact moment when SLBP (stem loop binding protein) is released during mRNA decay is currently unknown. (c) In Humans, ZCCHC11 in concert with Lin28 polyuridylates pre-let7-miRNA, which will then be degraded by DIS3L2 exonuclease. ZCCHC6 alone is responsible for the monouridylation of group II pre-miRNA, which will be further processed by Dicer. In the case of mature miRNA, ZCCHC11 monouridylates some miRNA leading to indirect consequences to the miRNA targeted mRNAs. (d) In plants, zebrafish, and flies, methylation and polyuridylation have antagonistic effects. Methylated siRNAs, piRNAs, and miRNAs will be stabilized whereas the polyuridylated one will be degraded.