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. Author manuscript; available in PMC: 2021 Apr 25.
Published in final edited form as: Chem Rev. 2017 Oct 12;118(8):4422–4447. doi: 10.1021/acs.chemrev.7b00462

Figure 5.

Figure 5.

Mtr4 helicase-containing complexes in human cells. (A) A complex resembling yeast TRAMP targets prematurely terminated ribosomal precursors for degradation by the nucleolar exosome71,72. (B) The NEXT complex recognizes short capped RNA polymerase II transcripts, such as PROMPTs, enhancer RNAs and precursors to snoRNAs and snRNAs, during transcription and targets them for degradation by the nuclear exosome72,151. (C) Following polyadenylation of longer RNA polymerase II transcripts by the canonical poly(A) polymerases PAPα and PAPγ, interaction of PAXT with the nascent ncRNAs targets them for degradation by the nuclear exosome152,153. A related complex, consisting of ZFC3H1and SKIV2L2/hMTR4 but lacking PABPN1, has also been described154.