title: The role of deadenylation in the degradation of unstable mRNAs in trypanosomes.
abstract: Removal of the poly(A) tail is the first step in the degradation of many eukaryotic mRNAs. In metazoans and yeast, the Ccr4/Caf1/Not complex has the predominant deadenylase activity, while the Pan2/Pan3 complex may trim poly(A) tails to the correct size, or initiate deadenylation. In trypanosomes, turnover of several constitutively-expressed or long-lived mRNAs is not affected by depletion of the 5'-3' exoribonuclease XRNA, but is almost completely inhibited by depletion of the deadenylase CAF1. In contrast, two highly unstable mRNAs, encoding EP procyclin and a phosphoglycerate kinase, PGKB, accumulate when XRNA levels are reduced. We here show that degradation of EP mRNA was partially inhibited after CAF1 depletion. RNAi-targeting trypanosome PAN2 had a mild effect on global deadenylation, and on degradation of a few mRNAs including EP. By amplifying and sequencing degradation intermediates, we demonstrated that a reduction in XRNA had no effect on degradation of a stable mRNA encoding a ribosomal protein, but caused accumulation of EP mRNA fragments that had lost substantial portions of the 5' and 3' ends. The results support a model in which trypanosome mRNAs can be degraded by at least two different, partially independent, cytoplasmic degradation pathways attacking both ends of the mRNA.
authors: Zentrum für Molekulare Biologie (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
authors: Angela
authors: A
authors: Schwede
authors: Theresa
authors: T
authors: Manful
authors: Bhaskar Anand
authors: BA
authors: Jha
authors: Claudia
authors: C
authors: Helbig
authors: Natalia
authors: N
authors: Bercovich
authors: Mhairi
authors: M
authors: Stewart
authors: Christine
authors: C
authors: Clayton
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000201:enzymology; D018503:Genome, Protozoan; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D010735:Phosphoglycerate Kinase / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D012260:Ribonucleases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014345:Trypanosoma / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: C406750:EP procyclin protein, Trypanosoma brucei; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D010735:Phosphoglycerate Kinase; D012260:Ribonucleases; C445084:mRNA deadenylase