Abrupt RNA changes precede the first cell division during the differentiation of Trypanosoma brucei bloodstream forms into procyclic forms in vitro

Pays, Étienne; Hanocq-Quertier, J.; Hanocq, Françoise; Assel, Suzanne Van; Nolan, Derek P.; Rolin, Sylvie

doi:10.1016/0166-6851(93)90163-r

Cited by 71 publications

(41 citation statements)

References 21 publications

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“…of total RNA per cell, whereas procyclic trypanosomes had 2.2-fold more RNA per cell. A previous estimate reported 0.8 pg per procyclic trypanosome (51). Depending on the growth conditions, Saccharomyces cerevisiae has 0.5-1.6 pg of RNA/cell, of which 85% is rRNA and 10% is tRNA and other small RNAs (52).…”

Section: Resultsmentioning

confidence: 93%

Control and Regulation of Gene Expression

Haanstra

Stewart

Luu

et al. 2008

Journal of Biological Chemistry

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Isoenzymes of phosphoglycerate kinase in Trypanosoma brucei are differentially expressed in its two main life stages. This study addresses how the organism manages to make sufficient amounts of the isoenzyme with the correct localization, which processes (transcription, splicing, and RNA degradation) control the levels of mRNAs, and how the organism regulates the switch in isoform expression. For this, we combined new quantitative measurements of phosphoglycerate kinase mRNA abundance, RNA precursor stability, trans splicing, and ribosome loading with published data and made a kinetic computer model. For the analysis of regulation we extended regulation analysis. Although phosphoglycerate kinase mRNAs are present at surprisingly low concentrations (e.g. 12 molecules per cell), its protein is highly abundant. Substantial control of mRNA and protein levels was exerted by both mRNA synthesis and degradation, whereas splicing and precursor degradation had little control on mRNA and protein concentrations. Yet regulation of mRNA levels does not occur by transcription, but by adjusting mRNA degradation. The contribution of splicing to regulation is negligible, as for all cases where splicing is faster than RNA precursor degradation.The flux through a metabolic pathway depends on the kinetic characteristics and concentrations of the constituent enzymes, on the levels of co-enzymes, and on their compartmentation. The concentrations of the enzymes in turn depend on the rates of transcription, processing, nuclear export, translation, degradation of the mRNA, and protein processing and degradation. Because each of these levels can in principle be regulated, the challenge is how to analyze the behavior of such a complex system in terms of the underlying processes.Metabolic control analysis (MCA) 4 and extensions that include gene expression is a powerful approach for the analysis of complex biochemical networks (1-4). In MCA, the control exerted by an enzyme on a concentration of any substance X (5) is quantified by its concentration control coefficient, which is defined as the percentage increase of the steady-state concentration of X that results from a 1% activation of the enzyme of interest. The sum of the concentration control coefficients of all the enzymes in the network is 0. This reflects that (i) activation of some enzymes increases the concentration of X, whereas activation of other enzymes should reduce the concentration of X (these enzymes have negative concentration control coefficients), and (ii) the positive controls together are equal to the negative controls. The principles of MCA do not only apply to metabolic pathways; they can also be used and extended to dissect the control distribution in regulatory pathways beyond steady state (for example see Refs.6 and 7) or gene expression cascades (for example see e.g. Ref. 8). Earlier MCA, as also applied to trypanosomes, has looked more at the control of fluxes, showing that usually flux control coefficients are smaller than 1, because several enzymes partially...

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Section: Resultsmentioning

confidence: 93%

Control and Regulation of Gene Expression

Haanstra

Stewart

Luu

et al. 2008

Journal of Biological Chemistry

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“…This result strongly suggested that the up-regulation exerted by the 3'-region of VSG mRNA in the bloodstream forms is due to an increase in steady-state levels of mRNA. In order to monitor the regulation conferred by the 3'-region of VSG mRNA during differentiation into the procyclic form, the bloodstream cell population was enriched in differentiation-competent stumpy forms by prolonged growth in immunosuppressed mice (Ziegelbauer et al, 1990;Pays et al, 1993). When incubated at 37°C in Baltz medium, which allows cultivation of bloodstream forms (Baltz et al, 1985), these cells showed the same CAT mRNA difference as found in proliferative bloodstream forms (slender forms) ( Figure 5, lanes 3-6 for two incubation periods, 10 min and 15 h).…”

Section: Resultsmentioning

confidence: 99%

The 3′-terminal region of the mRNAs for VSG and procyclin can confer stage specificity to gene expression in Trypanosoma brucei.

Berberof¹,

Vanhamme²,

Tebabi³

et al. 1995

The EMBO Journal

102

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The variant surface glycoprotein (VSG) and procyclin are the respective major surface antigens of the bloodstream and the procyclic forms of Trypanosoma brucei. These proteins and their mRNAs are both the most abundant and absolutely characteristic of their respective life cycle stages. We show that the 3'-terminal region of these mRNAs regulates expression of a reporter gene in an inverse manner, depending on the developmental form of the parasite. In the case of VSG mRNA, the 97 nt sequence upstream from the polyadenylation site is responsible for these effects. The regulation occurs through a variation of mRNA abundance which is not due to a change in primary transcription. In the bloodstream form this effect is manifested by an increase in RNA stability, whereas in the procyclic form it seems to be related to a reduction in the efficiency of mRNA maturation. The 3'-end of VSG mRNA can obviate the 5-to 10-fold stimulation of transcription driven by the procyclin promoter during differentiation from the bloodstream to the procyclic form. The predominance of posttranscriptional over transcriptional controls is probably linked to the organization of the trypanosome genome in polycistronic transcription units.

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“…Second, a defect in a process may not be visible when growth of the cells is reduced. For example, ribosomal RNA synthesis is closely coupled to cell growth in yeast and mammalian cells (see, for example, Warner 1999;Grummt 2003), and RNA synthesis is known to be repressed in stationary-phase trypanosomes (Pays et al 1993). If synthesis of an RNA is not occurring, defects in its processing will not be seen.…”

Section: Discussionmentioning

confidence: 99%

Roles of aTrypanosoma brucei5′→3′ exoribonuclease homolog in mRNA degradation

Irmer²,

Gudjonsdottir-Planck³

et al. 2006

RNA

100

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The genome of the kinetoplastid parasite Trypanosoma brucei encodes four homologs of the Saccharomyces cerevisiae 59/39 exoribonucleases Xrn1p and Xrn2p/Rat1p, XRNA, XRNB, XRNC, and XRND. In S. cerevisiae, Xrn1p is a cytosolic enzyme involved in degradation of mRNA, whereas Xrn2p is involved in RNA processing in the nucleus. Trypanosome XRND was found in the nucleus, XRNB and XRNC were found in the cytoplasm, and XRNA appeared to be in both compartments. XRND and XRNA were essential for parasite growth. Depletion of XRNA increased the abundances of highly unstable developmentally regulated mRNAs, perhaps by delaying a deadenylation-independent decay pathway. Degradation of more stable or unregulated mRNAs was not affected by XRNA depletion although a slight decrease in average poly(A) tail length was observed. We conclude that in trypanosomes 59/39 exonuclease activity is important in degradation of highly unstable, regulated mRNAs, but that for other mRNAs another step is more important in determining the decay rate.

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Abrupt RNA changes precede the first cell division during the differentiation of Trypanosoma brucei bloodstream forms into procyclic forms in vitro

Cited by 71 publications

References 21 publications

Control and Regulation of Gene Expression

Control and Regulation of Gene Expression

The 3′-terminal region of the mRNAs for VSG and procyclin can confer stage specificity to gene expression in Trypanosoma brucei.

Roles of aTrypanosoma brucei5′→3′ exoribonuclease homolog in mRNA degradation

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