The association of ACE gene D/I polymorphism with cardiovascular risk factors in a population from Rio de Janeiro

Our aim was to determine the frequencies of the angiotensin-converting enzyme (ACE) gene alleles D and I and any associations to cardiovascular risk factors in a population sample from Rio de Janeiro, Brazil. Eighty-four adults were selected consecutively during a 6-month period from a cohort subgroup of a previous large cross-sectional survey in Rio de Janeiro. Anthropometric data and blood pressure measurements, echocardiogram, albuminuria, glycemia, lipid profile, and ACE genotype and serum enzyme activity were determined. The frequency of the ACE*D and I alleles in the population under study, determined by PCR, was 0.59 and 0.41, respectively, and the frequencies of the DD, DI, and II genotypes were 0.33, 0.51, and 0.16, respectively. No association between hypertension and genotype was detected using the Kruskal-Wallis method. Mean plasma ACE activity (U/mL) in the DD (N = 28), DI (N = 45) and II (N = 13) groups was 43 (in males) and 52 (in females), 37 and 39, and 22 and 27, respectively; mean microalbuminuria (mg/dL) was 1.41 and 1.6, 0.85 and 0.9, and 0.6 and 0.63, respectively; mean HDL cholesterol (mg/dL) was 40 and 43, 37 and 45, and 41 and 49, respectively, and mean glucose (mg/dL) was 93 and 108, 107 and 98, and 85 and 124, respectively. A high level of ACE activity and albuminuria, and a low level of HDL cholesterol and glucose, were found to be associated with the DD genotype. Finally, the II genotype was found to be associated with variables related to glucose intolerance.

Trypanosoma cruzi: cloning and characterization of a RAB7 gene

The small monomeric GTP-binding proteins of the RAB subfamily are key regulatory elements of the machinery that controls membrane traffic in eukaryotic cells. These proteins have been localized to many different intracellular organelles, on both endocytic and exocytic compartments, suggesting that each step of vesicular traffic can involve a specific RAB protein. The presence of conserved amino acid domains in these proteins has allowed the cloning of their genes from several organisms, including yeast, plants, humans, and parasites. In this work we describe the identification, cloning, and characterization of a RAB7 gene homologue in Trypanosoma cruzi (TcRAB7). Our data indicate that this gene is present as a single copy in the T. cruzi genome, located on a 2.25-Mb chromosomal DNA. TcRAB7 is expressed in T. cruzi epimastigotes, metacyclic trypomastigotes, and spheromastigotes. We established transformed cell lines that express two versions of an epitope-tagged TcRAB7 protein: one wild type (pTAG) and one deleted at the C-terminal cysteines (pDeltaCXC). Wild-type TcRAB7 protein (pTAG) appears to be localized exclusively in the membrane fraction, while the mutated TcRAB7 protein (pDeltaCXC) loses the ability to associate with the membrane, showing only cytosolic localization. Also, we produced the recombinant TcRAB7 protein and demonstrated that it binds GTP. The identification of exo- and endocytic machinery components in T. cruzi and their function would provide specific markers of these subcellular compartments, thereby unveiling important aspects of vesicular traffic in this parasite.

Construction of a normalized cDNA library for the Trypanosoma cruzi genome project

Sequencing of the Trypanosoma cruzi genome is underway. Expressed sequence tags, obtained from cDNA libraries, facilitate mapping and gene discovery. The efficiency of large-scale generation of such tags is increased when using normalized cDNA libraries, where the frequency of individual clones is brought within a narrow range. Repetitive sequencing of abundant clones is therefore minimized. We constructed a normalized cDNA library from epimastigotes of clone CL Brener, and the efficiency of normalization of representative clones was assessed and shown to be adequate. The normalized cDNA library has been distributed to several groups and large-scale sequencing is currently in progress.

PARP promoter-mediated activation of a VSG expression site promoter in insect form Trypanosoma brucei

In trypanosomes the rRNA, PARP and VSG gene promoters mediate alpha-amanitin-resistant transcription of protein coding genes, presumably by RNA polymerase (pol) I. We compared the activity of PARP and VSG promoters integrated at one of the alleles of the largest subunit of pol II genes in insect form trypanosomes. Even though both promoters are roughly equally active in transient transformation assays in insect form trypanosomes, only the PARP promoter functioned effectively when integrated at the pol II largest subunit or other loci. Promoter activity in transient transformation assays is therefore not necessarily predictive of transcriptional activity once integrated into the trypanosome genome. The integrated fully active PARP promoter could upregulate in cis an otherwise poorly active integrated VSG promoter. The PARP promoter nucleotide sequence elements responsible for VSG promoter activation coincided with most of the important PARP promoter elements mapped previously by linker scanning mutagenesis, indicating that it is not a single unique promoter element that was responsible for VSG promoter activation. The data suggest that PARP promoter-mediated activation of the VSG promoter does not result from complementation of the VSG promoter with a single insect form-specific transcription factor whose binding site is missing from the VSG promoter and present in the PARP promoter. We favor a model in which chromatin structure at the locus is altered by the PARP promoter, allowing VSG promoter activation in insect form trypanosomes. We discuss the significance of these observations for the control of VSG promoters in insect form trypanosomes.

Transcriptional and post-transcriptional control of tubulin gene expression in Trypanosoma cruzi

We have shown that tubulin mRNA accumulation is regulated at the transcriptional level during metacyclogenesis of Trypanosoma cruzi, although the contribution of post-transcriptional mechanisms is also indicated. mRNA heterogeneity is not restricted to beta-tubulin, and differential regulation of alpha-tubulin mRNAs is observed during this stage of the parasite's life cycle. Treatment of epimastigotes with the microtubule-depolymerizing agent vinblastine resulted in growth inhibition and morphological alterations. Vinblastine also induced a rise in the pool of free tubulin subunits, concomitant with diminished tubulin synthesis and reduced mRNA levels. Tubulin gene transcription remained unaltered during vinblastine treatment, suggesting post-transcriptional control. These observations are in agreement with the autoregulatory model of tubulin gene expression described for a variety of cell types. We conclude that T. cruzi utilizes transcriptional and post-transcriptional control mechanisms for tubulin gene expression.

Alpha- and beta-tubulin mRNAs of Trypanosoma cruzi originate from a single multicistronic transcript

The cluster of alternated alpha- and beta-tubulin genes in the genome of Trypanosoma cruzi was shown to be transcribed into a single RNA molecule which upon processing gives rise to the mature alpha- and beta-tubulin mRNAs. This conclusion was based on: (i) nuclear RNA species with the same molecular mass hybridize to both alpha- and beta-tubulin cDNA probes; (ii) S1 nuclease assay of the clustered tubulin genes has shown protected DNA fragments of the same size and of greater molecular mass than that corresponding to the mRNAs, hybridizable to both alpha- and beta-tubulin cDNA probes; (iii) beta-tubulin hybrid selected RNA is still able to hybridize to alpha-tubulin probe.