Selective stabilization of mammalian microRNAs by 3′ adenylation mediated by the cytoplasmic poly(A) polymerase GLD-2

Abstract

The steady-state levels of microRNAs (miRNAs) and their activities are regulated by the post-transcriptional processes. It is known that 39 ends of several miRNAs undergo post-dicing adenylation or uridylation. We isolated the liver-specific miR-122 from human hepatocytes and mouse livers. Direct analysis by mass spectrometry revealed that one variant of miR-122 has a 39-terminal adenosine that is introduced after processing by Dicer. We identified GLD-2, which is a regulatory cytoplasmic poly(A) polymerase, as responsible for the 39-terminal adenylation of miR-122 after unwinding of the miR-122/ miR-122* duplex. In livers from GLD-2-null mice, the steady-state level of the mature form of miR-122 was specifically lower than in heterozygous mice, whereas no reduction of pre-miR-122 was observed, demonstrating that 39-terminal adenylation by GLD-2 is required for the selective stabilization of miR-122 in the liver.Supplemental material is available at http://www.genesdev.org.

PAPD5-mediated 3′ adenylation and subsequent degradation of miR-21 is disrupted in proliferative disease

“…Whereas miR-122 was previously shown to be stabilized by PAPD4-mediated adenylation of its 3′ end (19,20), we find instead that 3′ terminal addition by PAPD5 to miR-21 stimulates its degradation. This suggests the existence of a regulatory network of 3′ nucleotidyl transferases and exoribonucleases targeting specific mature miRNAs to enhance or prevent their degradation.…”

“…In this pathway, PAPD4 stabilizes the miRNA miR-122 by 3′ adenylation (19), thereby stimulating translational repression by miR-122 of the cytoplasmic polyadenylation element-binding protein CPEB. This protein binds to the 3′ UTR of TP53 mRNA and recruits PAPD5, which modulates the stability and translation of the TP53 mRNA by polyadenylating its 3′ end.…”

“…In human and murine liver cells, 3′ adenylation mediated by the nucleotidyl transferase PAPD4 has been shown to stabilize miR-122 (19). In contrast, PAPD5 was recently found to aid in the maturation of SNORA63 and other small nucleolar RNAs in a pathway where oligoadenylation by PAPD5 is followed by 3′-to-5′ trimming by the exonuclease PARN (38,39) (Fig.…”

“…Although several enzymes have been found to govern 3′ nucleotide addition to mature miRNAs (18), for most mature miRNAs 3′ adenylation is mediated by PAP associated domain containing 4 (PAPD4, also known as GLD2) (17). Whereas mature miR-122 is selectively stabilized by PAPD4-mediated adenylation (19), it remains unclear whether in general adenylation of the 3′ end of mature miRNAs increases their stability (17). miRNAs are involved in the regulation of many cellular processes including developmental and oncogenic pathways (3,20).…”

Inhibition of polyadenylation reduces inflammatory gene induction

“…They have a variety of substrates and functions, ranging from targeting aberrant transcripts for degradation in the nucleus to stabilizing microRNAs in the cytoplasm (Katoh et al 2009;Shcherbik et al 2010). Poly(A) polymerase a (PAPa, official gene name PAPOLA) is the best-studied family member and has been presumed to be the main poly(A) polymerase for the nuclear polyadenylation of mRNAs.…”