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Transcriptome-wide analysis of trypanosome mRNA decay reveals complex degradation kinetics and suggests a role for co-transcriptional degradation in determining mRNA levels

Abstract (Expand)

African trypanosomes are an excellent system for quantitative modelling of post-transcriptional mRNA control. Transcription is constitutive and polycistronic; individual mRNAs are excised by trans … splicing and polyadenylation. We here measure mRNA decay kinetics in two life cycle stages, bloodstream and procyclic forms, by transcription inhibition and RNASeq. Messenger RNAs with short half-lives tend to show initial fast degradation, followed by a slower phase; they are often stabilized by depletion of the 5'-3' exoribonuclease XRNA. Many longer-lived mRNAs show initial slow degradation followed by rapid destruction: we suggest that the slow phase reflects gradual deadenylation. Developmentally regulated mRNAs often show regulated decay, and switch their decay pattern. Rates of mRNA decay are good predictors of steady state levels for short mRNAs, but mRNAs longer than 3 kb show unexpectedly low abundances. Modelling shows that variations in splicing and polyadenylation rates can contribute to steady-state mRNA levels, but this is completely dependent on competition between processing and co-transcriptional mRNA precursor destruction.

Authors: , M. Ryten, D. Droll, , V. Farber, , C. Merce, , ,

Date Published: 26th Aug 2014

Publication Type: Not specified

The silicon trypanosome: a test case of iterative model extension in systems biology

Abstract (Expand)

The African trypanosome, Trypanosoma brucei, is a unicellular parasite causing African Trypanosomiasis (sleeping sickness in humans and nagana in animals). Due to some of its unique properties, it has … emerged as a popular model organism in systems biology. A predictive quantitative model of glycolysis in the bloodstream form of the parasite has been constructed and updated several times. The Silicon Trypanosome is a project that brings together modellers and experimentalists to improve and extend this core model with new pathways and additional levels of regulation. These new extensions and analyses use computational methods that explicitly take different levels of uncertainty into account. During this project, numerous tools and techniques have been developed for this purpose, which can now be used for a wide range of different studies in systems biology.

Authors: , , , , , , T. Papamarkou, , , , , , , ,

Date Published: 7th May 2014

Publication Type: Not specified

The role of the 5'-3' exoribonuclease XRNA in transcriptome-wide mRNA degradation

Abstract (Expand)

The steady-state level of each mRNA in a cell is a balance between synthesis and degradation. Here, we use high-throughput RNA sequencing (RNASeq) to determine the relationship between mRNA degradation … and mRNA abundance on a transcriptome-wide scale. The model organism used was the bloodstream form of Trypanosoma brucei, a protist that lacks regulation of RNA polymerase II initiation. The mRNA half-lives varied over two orders of magnitude, with a median half-life of 13 min for total (rRNA-depleted) mRNA. Data for poly(A)+ RNA yielded shorter half-lives than for total RNA, indicating that removal of the poly(A) tail was usually the first step in degradation. Depletion of the major 5'-3' exoribonuclease, XRNA, resulted in the stabilization of most mRNAs with half-lives under 30 min. Thus, on a transcriptome-wide scale, degradation of most mRNAs is initiated by deadenylation. Trypanosome mRNA levels are strongly influenced by gene copy number and mRNA half-life: Very abundant mRNAs that are required throughout the life-cycle may be encoded by multicopy genes and have intermediate-to-long half-lives; those encoding ribosomal proteins, with one to two gene copies, are exceptionally stable. Developmentally regulated transcripts with a lower abundance in the bloodstream forms than the procyclic forms had half-lives around the median, whereas those with a higher abundance in the bloodstream forms than the procyclic forms, such as those encoding glycolytic enzymes, had longer half-lives.

Authors: Theresa Manful, ,

Date Published: 26th Sep 2011

Publication Type: Not specified

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