PAPD5, a noncanonical poly(A) polymerase with an unusual RNA-binding motif.

Christiane Rammelt, Biter Bilen, Mihaela Zavolan, Walter Keller

Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, D-06099 Halle, Germany. christiane.rammelt@biochemtech.uni-halle.de

RNA (New York, N.Y.) 2011 Sep

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PAPD5 is one of the seven members of the family of noncanonical poly(A) polymerases in human cells. PAPD5 was shown to polyadenylate aberrant pre-ribosomal RNAs in vivo, similar to degradation-mediating polyadenylation by the noncanonical poly(A) polymerase Trf4p in yeast. PAPD5 has been reported to be also involved in the uridylation-dependent degradation of histone mRNA s. To test whether PAPD5 indeed catalyzes adenylation as well as uridylation of RNA substrates, we analyzed the in vitro properties of recombinant PAPD5 expressed in mammalian cells as well as in bacteria. Our results show that PAPD5 catalyzes the polyadenylation of different types of RNA substrates in vitro. Interestingly, PAPD5 is active without a protein cofactor, whereas its yeast homolog Trf4p is the catalytic subunit of a bipartite poly(A) polymerase in which a separate RNA-binding subunit is needed for activity. In contrast to the yeast protein, the C terminus of PAPD5 contains a stretch of basic amino acids that is involved in binding the RNA substrate.

Citation

Christiane Rammelt, Biter Bilen, Mihaela Zavolan, Walter Keller. PAPD5, a noncanonical poly(A) polymerase with an unusual RNA-binding motif. RNA (New York, N.Y.). 2011 Sep;17(9):1737-46