Genomic organization, transcription, splicing and gene regulation in<i>Leishmania</i>

Stiles, Jonathan K.; Hicock, Paul I.; Shah, Preetam H.; Meade, John C.

doi:10.1080/00034983.1999.11813485

Cited by 45 publications

(37 citation statements)

References 173 publications

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“…Therefore, we used a broader screening technique, namely, the mRNA differential display, to try to track mRNA species that are differentially expressed. Since Leishmania parasites produce polycistronic mRNAs and control gene expression at the level of mRNA processing and stability (46), one may ask how differential display PCR works to track differentially expressed mRNAs. If the overexpression of an mRNA is due to its higher stability, it will then be amplified by differential display, while a less stable (and hence less abundant) mRNA will be detected to a lesser extent.…”

Section: Discussionmentioning

confidence: 99%

Identification of a Disulfide Isomerase Protein ofLeishmania majoras a Putative Virulence Factor

et al. 2002

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Several approaches have been previously used to elucidate the genetic basis of Leishmania virulence. In general, they were based on laboratory Leishmania clones genetically modified or grown in the presence of selecting agents. In a previous study, we demonstrated that Leishmania major freshly isolated from human cutaneous lesions showed significant differences in the severity of the experimental disease induced in BALB/c mice. Here, using the mRNA differential display technique, we analyzed gene expression in L. major promastigotes showing different levels of virulence. We have identified a novel Leishmania gene encoding a 477-aminoacid protein exhibiting two distinct regions that are identical to the putative active-site sequence (CGHC) of the eukaryotic protein disulfide isomerase (PDI). The recombinant protein displayed a specific PDI enzymatic activity. This L. major disulfide isomerase protein (LmPDI) is predominantly expressed, at both the mRNA and protein levels, in highly virulent strains. Specific PDI inhibitors abolished the enzymatic activity of the recombinant protein and profoundly affected parasite growth. These findings suggest that LmPDI may play an important role in Leishmania natural pathogenicity and may constitute a new target for anti-Leishmania chemotherapy.

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Section: Discussionmentioning

confidence: 99%

Identification of a Disulfide Isomerase Protein ofLeishmania majoras a Putative Virulence Factor

et al. 2002

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“…probably proceeds unidirectionally (Myler et al, 1999) and is mostly constitutive: gene expression is regulated at the levels of RNA processing, RNA stability, and/or translation control (Curotto de Lafaille et al, 1992;Aly et al, 1994;Brandau et al, 1995;Graham, 1995;Teixeira, 1998;Stiles et al, 1999). Nevertheless, Hsp90 can obviously chaperone the factors involved at these levels of regulation as well.…”

Section: A Role For Hsp90 In Posttranscriptional Stress Responsementioning

confidence: 99%

Heat Shock Protein 90 Homeostasis Controls Stage Differentiation in Leishmania donovani

Wiesgigl

Clos

2001

MBoC

186

177

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The differentiation of Leishmania parasites from the insect stage, the promastigote, toward the pathogenic mammalian stage, the amastigote, is triggered primarily by the rise in ambient temperature encountered during the insect-to-mammal transmission. We show here that inactivation of heat shock protein (Hsp) 90, with the use of the drugs geldanamycin or radicicol, mimics transmission and induces the differentiation from the promastigote to the amastigote stage. Geldanamycin also induces a growth arrest of cultured promastigotes that can be forestalled by overexpression of the cytoplasmic Hsp90. Moreover, we demonstrate that Hsp90 serves as a feedback inhibitor of the cellular heat shock response in Leishmania. Our results are consistent with Hsp90 homeostasis serving as cellular thermometer for these primitive eukaryotes, controlling both the heat shock response and morphological differentiation. INTRODUCTIONProtozoan parasites of the genus Leishmania are transmitted by blood-feeding sand flies to mammalian hosts, including humans, whereby they encounter a rise in ambient temperature. Subjecting cultured insect stages, the promastigotes, of various Leishmania species to a similar temperature upshift in vitro results in the transient posttranscriptional upregulation of both heat shock protein (Hsp) 90 (also known as Hsp83) and Hsp70 synthesis and a persistent induction of Hsp100 expression Brandau et al., 1995;Krobitsch et al., 1998). Moreover, species such as L. mexicana, L. pifanoi, and L. donovani will, during heat stress and acidification of the medium, show a morphological transition toward the mammalian stage, the amastigote (Zilberstein and Shapira, 1994;Saar et al., 1998). Such axenic amastigotes are indistinguishable from true host tissue-derived intracellular amastigotes (Bates, 1993;Pan et al., 1993;Charest and Matlashewski, 1994;Charest et al., 1996;Gupta et al., 1996;Saar et al., 1998). Thus, the rise of temperature encountered during transmission can be viewed not as stress but rather as signal for cellular differentiation.We have shown previously that Hsp100 is critical for the expression of some amastigote stage-specific proteins and for overall virulence of the parasites (Hubel et al., 1997;Krobitsch et al., 1998); however, gene replacement mutants lacking Hsp100 still show, induced by elevated temperature, morphological differentiation to viable amastigote-like culture stages, indicating that the induction of morphological differentiation occurs independently or upstream of Hsp100 (Krobitsch et al., 1998;Krobitsch and Clos, 1999).Another chaperone, Hsp90 (Hsp83), is one of the most abundant proteins in Leishmania, constituting 2.8% of the cellular protein . Hsp90 (Hsp83) is encoded by multiple gene copies and is found in the soluble fraction of the cytoplasm (Shapira and Pinelli, 1989;Brandau et al., 1995;Hubel and Clos, 1996). Its sequence is distinct from the Grp94 homologue of L. infantum, which was characterized recently (Larreta et al., 2000). In higher eukaryotes and in yeast, cytosolic H...

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“…Trypanosomatid protozoans such as Leishmania have evolved cellular pathways that are fundamentally different from those of organisms that have been studied more extensively, such as bacteria, yeasts, and mammals (27). In trypanosomes, mature mRNAs are formed by processing of polycistronic pre-mRNAs.…”

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confidence: 99%

A Negative Regulatory Element Controls mRNA Abundance of the Leishmania mexicana Paraflagellar Rod Gene PFR2

et al. 2003

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The Leishmania mexicana PFR2 locus encodes a component of the paraflagellar rod (PFR), a flagellar structure found only in the insect stage of the life cycle. PFR2 mRNA levels are 10-fold lower in the mammalian stage than in the insect stage. Nuclear run-on experiments indicate that the change in PFR2 mRNA abundance is achieved posttranscriptionally. Deletion and block substitution analysis of the entire 1,400-nucleotide 3 untranslated region (UTR) of PFR2C led to the identification of a regulatory element contained within 10 nucleotides of the 3 UTR, termed the PFR regulatory element (PRE), that is necessary for the 10-fold regulation of PFR2 mRNA levels. Comparison of the half-lives of PFR2 transcripts, identical except for the presence or absence of the PRE, revealed that the PRE acts by destabilizing the PFR2 mRNA in amastigotes. The PRE was inserted into a construct which directs the constitutive expression of a chimeric PFR2 transcript. Insertion of the PRE resulted in regulated expression of this transcript, demonstrating that the regulatory element is sufficient for promastigote-specific expression. Since the PRE is present in the 3 UTR of all L. mexicana PFR genes examined so far, we propose that it serves a means of coordinating expression of PFR genes.

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Genomic organization, transcription, splicing and gene regulation inLeishmania

Cited by 45 publications

References 173 publications

Identification of a Disulfide Isomerase Protein ofLeishmania majoras a Putative Virulence Factor

Identification of a Disulfide Isomerase Protein ofLeishmania majoras a Putative Virulence Factor

Heat Shock Protein 90 Homeostasis Controls Stage Differentiation in Leishmania donovani

A Negative Regulatory Element Controls mRNA Abundance of the Leishmania mexicana Paraflagellar Rod Gene PFR2

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