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Biomedical subjects

L Selig

Publications and source records attributed to L Selig.

16 recordsLinked to original sources
PubMed2005

Latent tuberculosis infection among undergraduate medical students in Rio de Janeiro State, Brazil.

SETTING: Five medical schools in three cities with different tuberculosis (TB) incidence rates in Rio de Janeiro State, Brazil. OBJECTIVE: To estimate prevalence of and associated factors for latent tuberculosis infection (LTBI) among medical students. DESIGN: A cross-sectional survey was conducted among undergraduate students in pre-clinical, early and late clinical years from schools in cities with low (28/100,000), intermediate (63/100,000) and high (114/100,000) TB incidence rates. Information on socio-demographic profile, previous BCG vaccination, potential TB exposure, co-morbidity and use of respiratory protective masks was obtained. A tuberculin skin test (TST) was performed using the Mantoux technique by an experienced professional. A positive TST, defined as induration > or = 10 mm, was considered LTBI. RESULTS: LTBI prevalence was 6.9% (95%CI 5.4-8.6). In multivariate analysis, male sex (adjusted odds ratio [aOR] 1.8; 95% CI 1.1-3.0), late clinical years (aOR 1.9; 95% CI 1.01-3.5), intermediate TB incidence (aOR 4.3; 95% CI 1.3-14.6) and high TB incidence in the city of medical school (aOR 5.1; 95% CI 1.6-16.8) were significantly associated with LTBI. CONCLUSIONS: The higher prevalence of LTBI in late clinical years suggests that medical students are at increased risk for nosocomial Mycobacterium tuberculosis infection. The implementation of a TB control program may be necessary in medical schools, particularly in cities with higher TB incidence.

Adult↗
PubMed2003

The study of tuberculosis-attributed deaths as a tool for disease control planning in Rio de Janeiro, Brazil.

SETTING: Two tuberculosis (TB) reference hospitals and three general hospitals in Rio de Janeiro (RJ). OBJECTIVE: To analyze TB-attributed deaths as a tool for evaluating the TB control program in RJ. DESIGN: Retrospective study based on 302 medical records selected from the 1998 death database. RESULTS: Of 1146 registered adult (>14 years) TB-attributed deaths in RJ, 328 occurred in five hospitals, and 302 records were analyzed. Median age was 47.5 (17-89) years; 237 (78.5%) were male. Median time elapsed from onset of symptoms until diagnosis was 60 (7-730) days; median hospitalization was 60 (0-517) days. Acid-fast bacilli sputum smears were performed in 200 (69%) of 290 cases of pulmonary disease. Among 32 (36%) smear-negative patients, culture was done in only one. The recommended regimen (RHZ) was used in 175 (58%). Among 125 re-treatment patients, 55 (44%) were on RHZ instead of RHZE. Notification to health authorities was recorded in 131 (43.4%) cases. CONCLUSION: In RJ, young people die from TB. Major issues identified in the public health system were poor detection and notification and a high default rate, perpetuating the spread of TB. Treating professionals do not follow guidelines, and political commitment is needed to ensure TB control in the state and in the country.

Adolescent↗
PubMed2001

Interaction of human immunodeficiency virus type 1 Vpr with the HHR23A DNA repair protein does not correlate with multiple biological functions of Vpr.

The virion-associated Vpr protein of human immunodeficiency virus type 1 (HIV-1) alters cell cycle progression from the G2 phase, influences the virus in vivo mutation rate, and participates in the nuclear translocation of viral DNA. While many Vpr-interacting proteins have been identified, the functional relevance of these interactions remains to be thoroughly documented. We have explored the contribution of the interaction of HIV-1 Vpr with HHR23A, a cellular protein implicated in DNA repair, to the known phenotypes of Vpr. The association of Vpr with HHR23A required the core region of Vpr, which encompasses the two alpha-helical structures of the protein. No binding of HHR23A was detected with the Vpr and Vpx proteins of other primate lentiviruses. HIV-1 Vpr variants containing single amino acid substitutions in each alpha-helix and deficient for binding to HHR23A were isolated. The functional characterization of these Vpr variants indicated that binding to HHR23A did not correlate with the ability of Vpr to induce cell cycle arrest, even though it was previously proposed that HHR23A is a mediator of the Vpr-induced G2 arrest. Also, the Vpr-HHR23A interaction did not influence the HIV-1 in vivo mutation rate. Finally, Vpr and HHR23A are both localized in the nucleus, but no correlation was observed between the nuclear targeting of Vpr and the interaction with HHR23A. Further analysis is needed to determine the functional role(s) of the Vpr-HHR23A association during the HIV-1 life cycle.

Amino Acid Substitution↗
PubMed2001

The protein-protein interaction map of Helicobacter pylori.

With the availability of complete DNA sequences for many prokaryotic and eukaryotic genomes, and soon for the human genome itself, it is important to develop reliable proteome-wide approaches for a better understanding of protein function. As elementary constituents of cellular protein complexes and pathways, protein-protein interactions are key determinants of protein function. Here we have built a large-scale protein-protein interaction map of the human gastric pathogen Helicobacter pylori. We have used a high-throughput strategy of the yeast two-hybrid assay to screen 261 H. pylori proteins against a highly complex library of genome-encoded polypeptides. Over 1,200 interactions were identified between H. pylori proteins, connecting 46.6% of the proteome. The determination of a reliability score for every single protein-protein interaction and the identification of the actual interacting domains permitted the assignment of unannotated proteins to biological pathways.

Amino Acid Sequence↗
PubMed2000

Genome-wide protein interaction maps using two-hybrid systems.

Automated sequence technology has rendered functional biology amenable to genomic scale analysis. Among genome-wide exploratory approaches, the two-hybrid system in yeast (Y2H) has outranked other techniques because it is the system of choice to detect protein-protein interactions. Deciphering the cascade of binding events in a whole cell helps define signal transduction and metabolic pathways or enzymatic complexes. The function of proteins is eventually attributed through whole cell protein interaction maps where totally unknown proteins are partnered with fully annotated proteins belonging to the same functional category. Since its first description in the late 1980's, several versions of the Y2H have been developed in order to overcome the major limitations of the system, namely false positives and false negatives. Optimized versions have been recently applied at multi-molecular and genomic scale. These genome-wide surveys can be methodologically divided into two types of approaches: one either tests combinations of predefined polypeptides (the so-called matrix approach) using various short-cuts to speed up the process, or one screens with a given polypeptide (bait) for potential partners (preys) present in complex libraries of genomic or complementary DNA (library screening). In the former strategy, one tests what one knows, for example pair-wise interactions between full-length open reading frames from recently sequenced and annotated genomes. Although based on a one-by-one scheme, this method is reported to be amenable to large-scale genomics thanks to multicloning strategies and to the use of small robotics workstations. In the latter, highly complex cDNA or genomic libraries of protein domains can be screened to saturation with high-throughput screening systems allowing the discovery of yet unidentified proteins. Both approaches have strengths and drawbacks that will be discussed here. None yields a full proteome-wide screening since certain proteins (e.g. some transcription factors) are not usable in Y2H. Novel two-hybrid assays have been recently described in bacteria. Applications of these time- and cost-effective assays to genomic screening will be discussed and compared to the Y2H technology.

Animals↗
PubMed2000

The interaction of vpr with uracil DNA glycosylase modulates the human immunodeficiency virus type 1 In vivo mutation rate.

The Vpr protein of human immunodeficiency virus type 1 (HIV-1) influences the in vivo mutation rate of the virus. Since Vpr interacts with a cellular protein implicated in the DNA repair process, uracil DNA glycosylase (UNG), we have explored the contribution of this interaction to the mutation rate of HIV-1. Single-amino-acid variants of Vpr were characterized for their differential UNG-binding properties and used to trans complement vpr null mutant HIV-1. A striking correlation was established between the abilities of Vpr to interact with UNG and to influence the HIV-1 mutation rate. We demonstrate that Vpr incorporation into virus particles is required to influence the in vivo mutation rate and to mediate virion packaging of the nuclear form of UNG. The recruitment of UNG into virions indicates a mechanism for how Vpr can influence reverse transcription accuracy. Our data suggest that distinct mechanisms evolved in primate and nonprimate lentiviruses to reconcile uracil misincorporation into lentiviral DNA.

Animals↗
PubMed1999

Chicken ovalbumin upstream promoter-transcription factor II, a new partner of the glucose response element of the L-type pyruvate kinase gene, acts as an inhibitor of the glucose response.

Transcription of the L-type pyruvate kinase (L-PK) gene is induced by glucose in the presence of insulin and repressed by glucagon via cyclic AMP. The DNA regulatory sequence responsible for mediating glucose and cyclic AMP responses, called glucose response element (GlRE), consists of two degenerated E boxes spaced by 5 base pairs and is able to bind basic helix-loop-helix/leucine zipper proteins, in particular the upstream stimulatory factors (USFs). From ex vivo and in vivo experiments, it appears that USFs are required for correct response of the L-PK gene to glucose, but their expression and binding activity are not known to be regulated by glucose. A genetic screen in yeast has allowed us to identify a novel transcriptional factor binding to the GlRE, i.e. the chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII). Binding of COUP-TFII to the GlRE was confirmed by electrophoretic mobility shift assays, and COUP-TFII-containing complexes were detectable in liver nuclear extracts. Neither abundance nor binding activity of COUP-TFII appeared to be significantly regulated by diets. In footprinting experiments, two COUP-TFII-binding sites overlapping the E boxes were detected. Overexpression of COUP-TFII abrogated the USF-dependent transactivation of an artificial GlRE-dependent promoter in COS cells and the glucose responsiveness of the L-PK promoter in hepatocytes in primary culture. In addition, a mutated GlRE with increased affinity for USF and very low affinity for COUP-TFII conferred a dramatically decreased glucose responsiveness on the L-PK promoter in hepatocytes in primary culture by increasing activity of the reporter gene in low glucose condition. We propose that COUP-TFII could be a negative regulatory component of the glucose sensor complex assembled on the GlRE of the L-PK gene and most likely of other glucose-responsive genes as well.

Animals↗
PubMed1999

HEED, the product of the human homolog of the murine eed gene, binds to the matrix protein of HIV-1.

heed, the human homolog of mouse eed and Drosophila esc, two members of the trithorax (trx) and Polycomb group (Pc-G) of genes, was isolated by screening an activated lymphocyte cDNA library versus the immunodeficiency virus type 1 (HIV-1) MA protein used as a bait in a two-hybrid system in yeast. The human EED protein (HEED) had 99. 5% identity with the mouse EED protein and contained seven WD repeats. Two heed gene transcripts were identified, with a putative 407-nucleotide-long intron, giving rise to two HEED protein isoforms of 535 and 494 residues in length, respectively. The shorter HEED isoform, originated from the unspliced message, lacked the seventh WD repeat. HEED was found to bind to MA protein in vitro, as efficiently as in vivo in yeast cells. Site-directed mutagenesis and phage biopanning suggested that the interaction between HEED and MA involved the N-terminal region of the MA protein, including the first polybasic signal, in a MA conformation-dependent manner. In the HEED protein, however, two discrete linear MA-binding motifs were identified within residues 388-403, overlapping the origin of the fifth WD repeat. Deletion of the C-terminal 41 residues of HEED, spanning the seventh WD repeat, as in the 494-residue HEED protein, was detrimental to HEED-MA interaction in vivo, suggesting the existence of another C-terminal binding site and/or a conformational role of the HEED C-terminal domain in the MA-HEED interaction. MA and HEED proteins co-localized within the nucleus of co-transfected human cells and of recombinant baculovirus co-infected insect cells. This and the failure of HEED to bind to uncleaved GAG precursor suggested a role of HEED at the early stages of virus infection, rather than late in the virus life cycle.

Amino Acid Sequence↗
PubMed1999

Interaction with the p6 domain of the gag precursor mediates incorporation into virions of Vpr and Vpx proteins from primate lentiviruses.

Vpr and Vpx proteins from human and simian immunodeficiency viruses (HIV and SIV) are incorporated into virions in quantities equivalent to those of the viral Gag proteins. We demonstrate here that Vpr and Vpx proteins from distinct lineages of primate lentiviruses were able to bind to their respective Gag precursors. The capacity of HIV type 1 (HIV-1) Vpr mutants to bind to Pr55(Gag) was correlated with their incorporation into virions. Molecular analysis of these interactions revealed that they required the C-terminal p6 domain of the Gag precursors. While the signal for HIV-1 Vpr binding lies in the leucine triplet repeat region of the p6 domain reported to be essential for incorporation, SIVsm Gag lacking the equivalent region still bound to SIVsm Vpr and Vpx, indicating that the determinants for Gag binding are located upstream of this region of the p6 domain. Binding to Gag cleavage products showed that HIV-1 Vpr interacted directly with the nucleocapsid protein (NC), whereas SIVsm Vpr and Vpx did not interact with NC but with the p6 protein. These results (i) reveal differences between HIV-1 and SIVsm for the p6 determinants required for Vpr and Vpx binding to Gag and (ii) suggest that HIV-1 Vpr and SIVsm Vpr and Vpx interact with distinct cleavage products of the precursor following proteolytic processing in the virions.

Amino Acid Sequence↗
PubMed1999

Mutational analysis of Vpr-induced G2 arrest, nuclear localization, and cell death in fission yeast.

Cell cycle G2 arrest, nuclear localization, and cell death induced by human immunodeficiency virus type 1 Vpr were examined in fission yeast by using a panel of Vpr mutations that have been studied previously in human cells. The effects of the mutations on Vpr functions were highly similar between fission yeast and human cells. Consistent with mammalian cell studies, induction of cell cycle G2 arrest by Vpr was found to be independent of nuclear localization. In addition, G2 arrest was also shown to be independent of cell killing, which only occurred when the mutant Vpr localized to the nucleus. The C-terminal end of Vpr is crucial for G2 arrest, the N-terminal alpha-helix is important for nuclear localization, and a large part of the Vpr protein is responsible for cell killing. It is evident that the overall structure of Vpr is essential for these cellular effects, as N- and C-terminal deletions affected all three cellular functions. Furthermore, two single point mutations (H33R and H71R), both of which reside at the end of each alpha-helix, disrupted all three Vpr functions, indicating that these two mutations may have strong effects on the overall Vpr structure. The similarity of the mutant effects on Vpr function in fission yeast and human cells suggests that fission yeast can be used as a model system to evaluate these Vpr functions in naturally occurring viral isolates.

Cell Death↗
PubMed1998

A novel human WD protein, h-beta TrCp, that interacts with HIV-1 Vpu connects CD4 to the ER degradation pathway through an F-box motif.

HIV-1 Vpu interacts with CD4 in the endoplasmic reticulum and triggers CD4 degradation, presumably by proteasomes. Human beta TrCP identified by interaction with Vpu connects CD4 to this proteolytic machinery, and CD4-Vpu-beta TrCP ternary complexes have been detected by coimmunoprecipitation. beta TrCP binding to Vpu and its recruitment to membranes require two phosphoserine residues in Vpu essential for CD4 degradation. In beta TrCP, WD repeats at the C terminus mediate binding to Vpu, and an F box near the N terminus is involved in interaction with Skp1p, a targeting factor for ubiquitin-mediated proteolysis. An F-box deletion mutant of beta TrCP had a dominant-negative effect on Vpu-mediated CD4 degradation. These data suggest that beta TrCP and Skp1p represent components of a novel ER-associated protein degradation pathway that mediates CD4 proteolysis.

Binding Sites↗
PubMed1997

Binding of HIV-1 Nef to a novel thioesterase enzyme correlates with Nef-mediated CD4 down-regulation.

Nef is a 27-kDa myristoylated protein conserved in primate lentiviruses. In vivo, simian immunodeficiency virus Nef is required in macaques to produce a high viral load and full pathological effects. Nef has at least three major effects in vitro, induction of CD4 down-regulation, alteration of T cell activation pathways, and enhancement of viral infectivity. We have used the yeast two-hybrid system to identify cellular proteins that interact with HIV-1Lai Nef and could mediate Nef function. A human cDNA was isolated that encodes a new type of thioesterase, an enzyme that cleaves thioester bonds. This novel thioesterase is unlike the animal types I and II thioesterases previously cloned but is homologous to the Escherichia coli thioesterase II. Nef and this thioesterase interact in vitro and are co-immunoprecipitated by anti-Nef antibodies in CEM cells expressing Nef. Nef alleles from human immunodeficiency virus-1 (HIV-1) isolates unable to down-regulate CD4 do not react or react poorly with thioesterase. An HIV-1 NefLai mutant selected for its lack of interaction with thioesterase was also unable to down-regulate CD4 cell-surface expression. These observations suggest that this human thioesterase is a cellular mediator of Nef-induced CD4 down-regulation.

Alleles↗
PubMed1997

Uracil DNA glycosylase specifically interacts with Vpr of both human immunodeficiency virus type 1 and simian immunodeficiency virus of sooty mangabeys, but binding does not correlate with cell cycle arrest.

The Vpr protein encoded by human immunodeficiency virus type 1 (HIV-1) is important for growth of virus in macrophages and prevents infected cells from passing into mitosis (G2 arrest). The cellular target for these functions is not known, but Vpr of HIV-1 and the related Vpr from simian immunodeficiency virus of sooty mangabeys (SIV(SM)) bind the DNA repair enzyme UNG, while the Vpx protein of SIV(SM) does not. Nonetheless, a mutational analysis of Vpr showed that binding to UNG is neither necessary nor sufficient for the effect of Vpr on the cell cycle.

Amino Acid Sequence↗
PubMed1997

Pleural tuberculosis and human immunodeficiency virus co-infection.

SETTING: Department of internal medicine in a general hospital in Rio de Janeiro, Brazil, which provides secondary care to the poor population. OBJECTIVE: The aim of this study was to evaluate the prevalence of human immunodeficiency virus (HIV) infection in patients with pleural tuberculosis (TB) and to compare its manifestations in HIV-negative and HIV-infected patients. DESIGN: Cross-sectional study. METHODS: Forty-three patients with a final diagnosis of pleural TB were submitted to HIV testing (ELISA), chest X-ray, and thoracentesis for biochemical, cytological and bacteriological analysis. Pleural tissue was obtained in 36 patients for histopathological examination. PPD testing was performed in 29 patients. Whenever productive cough was present, sputum acid-fast smears and culture for Mycobacterium tuberculosis were performed. RESULTS: The HIV prevalence was high (30%). TB symptoms were similar in both groups. Atypical radiological aspects were observed in HIV-infected patients with concurrent pulmonary TB (P = 0.03). Pleural fluid, tissue aspects and PPD testing were comparable in both groups. CONCLUSION: Only atypical radiographic patterns in patients with concurrent pulmonary TB were indicative of HIV infection. Therefore, a high index of suspicion is necessary for the early recognition of HIV/TB co-infection. We suggest that all patients presenting with pleural TB should be screened for anti-HIV antibodies.

AIDS-Related Opportunistic Infections↗