Leishmania amazonensis: Partial purification and study of the biochemical properties of the telomerase reverse transcriptase activity from promastigote-stage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The putative telomerase reverse transcriptase component of Leishmania amazonensis: gene cloning and characterization

The Leishmania amazonensis telomerase gene was cloned by a polymerase chain reaction-based strategy using primers designed from a Leishmania major sequence that shared similarities with conserved telomerase motifs. The genes from three other species were cloned for comparative purposes. A ClustalW multiple-sequence alignment demonstrated that the Leishmania telomerases show greater homology with each other than with the proteins of other kinetoplastids and eukaryotes. Characterization experiments indicated that the putative Leishmania telomerase gene was probably in single copy and located in the largest chromosomes. A single messenger ribonucleic acid transcript was found in promastigotes. Phylogenetic analysis suggested that Leishmania telomerase might represent a liaison between the oldest and the newest branches of telomerases.

Telomerase activity in the vaginal margins of radical hysterectomy in patients with carcinoma of the cervix: Correlation with histology and human papillomavirus

This study was undertaken to evaluate the telomerase activity both in the tumor and in the vaginal margins of radical hysterectomy in patients with squamous cell carcinoma (SCC) of the cervix. Thirty-three patients with SCC of the cervix (study group) and 13 patients with uterine myoma (control group) were prospectively studied. Tissue samples were taken from the tumor or cervix, anterior vaginal margin (AVM), and posterior vaginal margin (PVM). The specimens were analyzed by histopathology, by a telomerase PCR-TRAP-ELISA kit, and by polymerase chain reaction using human papillomavirus (HPV) DNA. The telomerase activity was significantly higher in the tumor than in the benign cervix (P < 0.001). There was no difference in telomerase activity in the AVM and PVM in patients with cervical carcinoma compared to the control group. Telomerase activity was associated with the presence of histologic malignancy in the PVM of patients submitted to radical hysterectomy (P = 0.03). This association was not observed with the presence of HPV in AVM or PVM in the study group. Telomerase activity is a marker of histologic malignancy in patients with SCC of the cervix. There was no association between the telomerase activity and the presence of HPV in vaginal margins of patients submitted to radical hysterectomy. © 2006, Copyright the Authors.

Missing association between telomerase activity and clinicopathological features in patients with early stage carcinoma of the cervix

Objectives: This study was undertaken to evaluate the association between the telomerase activity in the tumor and clinicopathological findings in patients with stage IB-IIA (FIGO) carcinoma of the cervix. Methods: Thirty-eight patients with carcinoma of the cervix submitted to radical hysterectomy were prospectively from January 1998 to November 2001. Samples from the tumor were taken and analyzed by the telomerase PCR-TRAP-ELISA kit. Clinicopathological characteristics such as age, stage, tumor size, grade of differentiation, lymphatic vascular space invasion (LVSI), parametrial involvement and status of pelvic lymph nodes were also recorded. Results: Patient's mean age was 49.3 ± 1.99 years (29-76 years). The clinical stage (FIGO) was IB in 35 patients (92.1%) and IIA in 3 patients (7.9%). The histological classification identified squamous cell carcinoma in 33 patients (86.8%) and adenocarcinoma in 5 patients (13.2%). There was no association between age, clinical stage, histological classification, tumor size, grade of differentiation and presence of LVSI with tumoral telomerase activity. The telomerase activity was not associated with the presence of vaginal involvement (P = 0.349), parametrium involvement (P = 0.916), pelvic lymph node metastasis (P = 0.988) or tumoral recurrence (P = 0.328) in patients with carcinoma of the cervix. Conclusions: Telomerase activity in the tumor is not associated with clinicopathological findings or tumor recurrence in patients with early stage cervical carcinoma. © 2006 Springer-Verlag.

Telomere and Telomerase Biology

Telomeres are the physical ends of eukaryotic linear chromosomes. Telomeres form special structures that cap chromosome ends to prevent degradation by nucleolytic attack and to distinguish chromosome termini from DNA double-strand breaks. With few exceptions, telomeres are composed primarily of repetitive DNA associated with proteins that interact specifically with double- or single-stranded telomeric DNA or with each other, forming highly ordered and dynamic complexes involved in telomere maintenance and length regulation. In proliferative cells and unicellular organisms, telomeric DNA is replicated by the actions of telomerase, a specialized reverse transcriptase. In the absence of telomerase, some cells employ a recombination-based DNA replication pathway known as alternative lengthening of telomeres. However, mammalian somatic cells that naturally lack telomerase activity show telomere shortening with increasing age leading to cell cycle arrest and senescence. In another way, mutations or deletions of telomerase components can lead to inherited genetic disorders, and the depletion of telomeric proteins can elicit the action of distinct kinases-dependent DNA damage response, culminating in chromosomal abnormalities that are incompatible with life. In addition to the intricate network formed by the interrelationships among telomeric proteins, long noncoding RNAs that arise from subtelomeric regions, named telomeric repeat-containing RNA, are also implicated in telomerase regulation and telomere maintenance. The goal for the next years is to increase our knowledge about the mechanisms that regulate telomere homeostasis and the means by which their absence or defect can elicit telomere dysfunction, which generally results in gross genomic instability and genetic diseases.

The putative Leishmania telomerase RNA (leishTER) undergoes trans-splicing and contains a conserved template sequence

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Telomere biology of trypanosomatids: beginning to answer some questions

Studies of telomere structure and maintenance in trypanosomatids have provided insights into the evolutionary origin and conservation of some telomeric components shared by trypanosomes and vertebrates. For example, trypanosomatid telomeres are maintained by telomerase and consist of the canonical TTAGGG repeats, which in Trypanosoma brucei can form telomeric loops (t-loops). However, the telomeric chromatin of trypanosomatids is composed of organ ism-specific proteins and other proteins that share little sequence similarity with their vertebrate counterparts. Because telomere maintenance mechanisms are essential for genome stability, we propose that the particular features shown by the trypanosome telomeric chromatin hold the key for the design of antiparasitic drugs.

Leishmania replication protein A-1 binds in vivo single-stranded telomeric DNA

Replication protein A (RPA) is a highly conserved heterotrimeric single-stranded DNA-binding protein involved in different events of DNA metabolism. In yeast, subunits 1 (RPA-1) and 2 (RPA-2) work also as telomerase recruiters and, in humans, the complex unfolds G-quartet structures formed by the 3' G-rich telomeric strand. In most eukaryotes, RPA-1 and RPA-2 bind DNA using multiple OB fold domains. In trypanosomatids, including Leishmania, RPA-1 has a canonical OB fold and a truncated RFA-1 structural domain. In Leishmania amazonensis, RPA-1 alone can form a complex in vitro with the telomeric G-rich strand. In this work, we show that LaRPA-1 is a nuclear protein that associates in vivo with Leishmania telomeres. We mapped the boundaries of the OB fold DNA-binding domain using deletion mutants. Since Leishmania and other trypanosomatids lack homologues of known telomere end binding proteins, our results raise questions about the function of RPA-1 in parasite telomeres. (C) 2007 Elsevier B.V. All rights reserved.

Isolation and characterization of Wharton's jelly-derived multipotent mesenchymal stromal cells obtained from bovine umbilical cord and maintained in a defined serum-free three-dimensional system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genomic and phenotypic profiles of two Brazilian breast cancer cell lines derived from primary human tumors

Breast cancer is the most common type of cancer among women worldwide. Research using breast cancer cell lines derived from primary tumors may provide valuable additional knowledge regarding this type of cancer. Therefore, the aim of this study was to investigate the phenotypic profiles of MACL-1 and MGSO-3, the only Brazilian breast cancer cell lines available for comparative studies. We evaluated the presence of hormone receptors, proliferation, differentiation and stem cell markers, using immunohistochemical staining of the primary tumor, cultured cells and xenografts implanted in immunodeficient mice. We also investigated the ability of the cell lines to form colonies and copy number alterations by array comparative genomic hybridization. Histopathological analysis showed that the invasive primary tumor from which the MACL-1 cell line was derived, was a luminal A subtype carcinoma, while the ductal carcinoma in situ (DCIS) that gave rise to the MGSO-3 cell line was a HER2 subtype tumor, both showing different proliferation levels. The cell lines and the tumor xenografts in mice preserved their high proliferative potential, but did not maintain the expression of the other markers assessed. This shift in expression may be due to the selection of an 'establishment' phenotype in vitro. Whole-genome DNA evaluation showed a large amount of copy number alterations (CNAs) in the two cell lines. These findings render MACL-1 and MGSO-3 the first characterized Brazilian breast cancer cell lines to be potentially used for comparative research. © 2013 Spandidos Publications Ltd. All rights reserved.

Avaliação da população de células tronco tumorais nas neoplasias da glândula mamária em cadelas

Pós-graduação em Ciência Animal - FMVA

Verificação da formação de complexos protéicos nos telômeros de L. amazonensis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo das interações in vivo entre as proteínas teloméricas LaRPA-1 e LaRbp38 usando o sistema do duplo híbrido

A leishmaniose é um conjunto de doenças infecciosas causadas por parasitas do gênero Leishmania, que afligem milhões de pessoas no mundo, tendo a cada ano dois milhões de novos casos e 70 mil mortes. As drogas utilizadas no tratamento das diferentes formas clínicas da doença apresentam alta toxicidade e baixa eficácia, além de apresentarem muitos efeitos colaterais e colaborarem com o aparecimento de parasitas e vetores resistentes. Devido a estas adversidades, o desenvolvimento de novas terapias para o tratamento desta parasitose é incentivada pela Organização Mundial da Saúde (OMS) e um maior conhecimento sobre a biologia molecular destes protozoários poderá facilitar estas descobertas. Ultimamente, os telômeros, estruturas nucleoproteícas nos terminais dos cromossomos de eucariotos, têm sido alvo intenso de estudos, que visam utilizá-los como alvo terapêutico contra tumores malignos e microrganismos patogênicos. Os telômeros geralmente se apresentam como estruturas dinâmicas onde ocorrem interações entre o DNA e proteínas, resultando na formação do complexo telomérico, que é responsável pela proteção e manutenção dos cromossomos e estabilidade do genoma, caracterizando uma função imprescindível para viabilidade celular. Componentes do complexo telomérico de Leishmania amazonensis foram identificados por ensaios bioquímicos em extratos positivos para a atividade de telomerase. Entre estes componentes identificou-se as proteínas LaRPA-1 (L. amazonensis Replication Protein A-1) e a LaRbp38 (L. amazonensis RNA binding protein) as quais mostraram habilidade de interagir com o DNA telomérico in vitro e in vivo. Mais recentemente, utilizando-se ensaios de imunoprecipitação e de captura por “pull-down” foi demonstrado que estas proteínas fazem parte de um mesmo complexo nos telômeros do parasita. Este trabalho pretende confirmar estas possíveis interações entre as proteínas teloméricas LaRPA-1 e ...

Análise da expressão de genes oncogênicos selecionados do KSHV em células endoteliais TIVE-LTC co-cultivadas com células linfóides Jurkat com e sem expressão constitutiva da proteína tat do HIV-1

O Herpesvírus associado ao sarcoma de Kaposi (KSHV), ou Herpesvírus Humano tipo 8 (HHV-8), é o agente etiológico do sarcoma de Kaposi (SK), uma neoplasia maligna vascular. O ciclo biológico do KSHV apresenta duas fases, denominadas ciclo latente e ciclo lítico (ou produtivo). O ciclo latente é marcado pela expressão de um número reduzido de genes virais, com destaque para LANA e vFLIP. No ciclo lítico ocorre a replicação do genoma viral e a produção de novas partículas virais infecciosas; dentre seus principais produtos destacam-se as proteínas Rta, vGPCR e K1. LANA, vFLIP, vGPCR e K1 apresentam propriedades oncogênicas relatadas na literatura, enquanto Rta têm papel importante na regulação da transição entre os ciclos lítico e latente do KSHV. O KSHV é requerido para o desenvolvimento do SK. No entanto, a infecção pelo vírus não é suficiente para o desenvolvimento da doença. Por outro lado, sabe-se que o HIV é um co-fator importante, que favorece o desenvolvimento dessa neoplasia. Sugere-se que a proteína tat do HIV-1 amplifica a infectividade do KSHV, hiper-regulando a expressão de diferentes genes herpesvirais e colaborando para o crescimento e sobrevivência de células endoteliais que compõem as lesões do SK. A fim de contribuir para um melhor entendimento dos efeitos da proteína tat do HIV-1 em células infectadas pelo KSHV, o presente trabalho descreveu eventuais alterações na expressão dos genes codificadores de vFLIP, LANA, vGPCR, Rta e K1 em células endoteliais de veia umbilical humana imortalizada pela telomerase e infectada pelo KSHV a longo prazo (TIVE-LTCs) expostas à proteína tat do HIV-1 produzida por células linfóides T (CLTs) em co-cultivo. Células Jurkat contendo ou não vetor da proteína tat do HIV-1 foram utilizadas como CLTs e co-cultivadas com TIVE-LTCs por 48, 72 e 96 horas. Após extração do RNA total das...(Resumo completo, clicar acesso eletrônico abaixo)

Clonagem, expressão e purificação de três mutantes truncados da proteína LaRPA-1 de Leishmania amazonensis

A leishmaniose é uma doença que atinge milhões de pessoas no mundo e, de acordo com a FUNASA, está se espalhando por todas as regiões do Brasil. O tratamento desta zoonose é ineficaz, pois os fármacos utilizados apresentam muitos efeitos colaterais e colaboram com o aparecimento de parasitas e vetores resistentes. Portanto um maior conhecimento sobre a biologia molecular destes protozoários poderá facilitar o descobrimento de novas terapias e desenvolvimento de drogas antiparasitárias. O complexo telomérico é formado pela interação de DNA com proteínas, sendo que estas últimas podem também interagir entre si. A proteína RPA de eucariotos compreende um complexo trimérico subdividido em três subunidades. Este cumpre independentemente ou juntamente com outras proteínas diversas funções vitais para a célula, entre elas, auxiliar na manutenção dos telômeros e ajudar a recrutar a telomerase. Além disso, ela parece ser um dos principais componentes do complexo de proteínas que interagem com o terminal simples fita telomérico de protozoários tripanosomatídeos. Curiosamente, em Leishmania spp., as subunidades 2 e 3, ao contrário da subunidade 1 da RPA, não fazem parte do complexo telomérico. Portanto a LaRPA-1 pode apresentar comportamentos peculiares quando comparada a RPA dos outros eucariotos, e se tornar um importante alvo ao se estudar a biologia molecular do parasita. Este trabalho tem como objetivo clonar, expressar e purificar os três diferentes mutantes truncados da proteína LaRPA-1 para, futuramente, utilizar-se estas proteínas recombinantes como ligantes em ensaios de interação proteína:proteína, visando mapear possíveis sítios ou domínios na proteína LaRPA-1.O gene que codifica LaRPA-1 já encontrava-se clonado e sequenciado no laboratório de Telômeros da UNESP de Botucatu....(Resumo completo, clicar acesso eletrônico abaixo)