Figure S6: Adenylation by PAPD5 and trimming by PARN of SNORA63 (small nucleolar RNA, H/ACA box 63).
As part of the maturation pathway of SNORA63 and other small nucleolar RNAs (snoRNAs), oligoadenylation of the 3’ end of the snoRNA by PAPD5 is followed by 3’-to-5’ trimming by the exonuclease PARN to produce the mature snoRNA [S1, S2]. Interestingly, 7 nt near the 3’ end of miR-21 are identical to a stretch of nucleotides that span the exon-intron boundary at the 3’ end of the immature SNORA63 transcript. However, we did not find this sequence pattern at the 3’ end of miR-142-3p, the only other apparent miRNA target of PAPD5 in our data, nor in the other snoRNAs targeted by PAPD5.
 
S1. Berndt H, et al. (2012) Maturation of mammalian H/ACA box snoRNAs: PAPD5-dependent adenylation and PARN-dependent trimming. RNA 18(5):958-972.
S2. Virtanen A, Henriksson N, Nilsson P, Nissbeck M (2013) Poly(A)-specific ribonuclease (PARN): An allosterically regulated, processive and mRNA cap-interacting deadenylase. Crit Rev Biochem Mol Biol 48(2):192-209.