ABSTRACT
Noncoding circular RNAs are widespread in the tree of life. Particularly, intron-containing circular RNAs which apparently upregulate their parental gene expression. Entamoeba histolytica, the causative agent of dysentery and liver abscesses in humans, codes for several noncoding RNAs, including circular ribosomal RNAs, but no intron containing circular RNAs have been described to date. Divergent RT-PCR and diverse molecular approaches, allowed us to detect bona fide full-length intronic circular RNA (flicRNA) molecules. Self-splicing reactions, RNA polymerase II inhibition with Actinomycin D, and second step of splicing-inhibition with boric acid showed that the production of flicRX13 (one of the flicRNAs found in this work, and our test model) depends on mRNA synthesis and pre-mRNA processing instead of self-splicing. To explore the cues and factors involved in flicRX13 biogenesis in vivo, splicing assays were carried out in amoeba transformants where splicing factors and Dbr1 (intron lariat debranching enzyme 1) were silenced or overexpressed, or where Rabx13 wild-type and mutant 5'ss (splice site) and branch site minigene constructs were overexpressed. Whereas SF1 (splicing factor 1) is not involved, the U2 auxiliary splicing factor, Dbr1, and the GU-rich 5'ss are involved in postsplicing flicRX13 biogenesis, probably by Dbr1 stalling, in a similar fashion to the formation of ciRNAs (circular intronic RNAs), but with distinctive 5'-3'ss ligation points. Different from the reported functions of ciRNAs, the 5'ss GU-rich element of flicRX13 possibly interacts with transcription machinery to silence its own gene in cis. Furthermore, introns of E. histolytica virulence-related genes are also processed as flicRNAs.
Subject(s)
Entamoeba histolytica/genetics , Entamoeba histolytica/metabolism , Introns , RNA Splicing , RNA/genetics , RNA/metabolism , Gene Silencing , RNA Splicing Factors/genetics , RNA Splicing Factors/metabolism , RNA, CircularABSTRACT
The RNA lariat debranching enzyme (Dbr1) has different functions in RNA metabolism, such as hydrolyzing the 2'-5' linkage in intron lariats, positively influencing Ty1 and HIV-1 retrotransposition, and modulating snRNP recycling during splicing reactions. It seems that Dbr1 is one of the major players in RNA turnover. It is remarkable that of all the studies carried out to date with Dbr1, to our knowledge, none of them have evaluated the expression profile of the endogenous Dbr1 gene. In this work, we describe, for the first time, that Entamoeba histolytica EhDbr1 mRNA has a very short half-life (less than 30 min) and encodes a very stable protein that is present until trophozoite cultures die. We also show that the EhDbr1 protein is present in the nuclear periphery on the cytoplasmic basal side, contrary to the localization of human Dbr1. Comparing these results with previous hypotheses and with results from different organisms suggests that Dbr1 gene expression is finely tuned and conserved across eukaryotes. Experiments describing the aspects of Dbr1 gene expression and Dbr1 mRNA turnover as well as other functions of the protein need to be performed. Particularly, a special emphasis is needed on the protozoan parasite E. histolytica, the causative agent of amoebiasis, since even though it is a unicellular organism, it is an intron-rich eukaryote whose intron lariats seem to be open to avoid intron lariat accumulation and to process them in non-coding RNAs that might be involved in its virulence.
Subject(s)
Entamoeba histolytica/enzymology , Entamoeba histolytica/genetics , Gene Expression Regulation , RNA Nucleotidyltransferases/genetics , RNA Nucleotidyltransferases/metabolism , Cell Nucleus/enzymology , Enzyme Stability , Gene Expression Profiling , RNA Nucleotidyltransferases/chemistry , RNA StabilityABSTRACT
OBJECTIVE: To present the Brazilian Neuromyelitis Optica Database System (NMO-DBr), a database system which collects, stores, retrieves, and analyzes information from patients with NMO and NMO-related disorders. METHOD: NMO-DBr uses Flux, a LIMS (Laboratory Information Management Systems) for data management. We used information from medical records of patients with NMO spectrum disorders, and NMO variants, the latter defined by the presence of neurological symptoms associated with typical lesions on brain magnetic resonance imaging (MRI) or aquaporin-4 antibody seropositivity. RESULTS: NMO-DBr contains data related to patient's identification, symptoms, associated conditions, index events, recurrences, family history, visual and spinal cord evaluation, disability, cerebrospinal fluid and blood tests, MRI, optic coherence tomography, diagnosis and treatment. It guarantees confidentiality, performs cross-checking and statistical analysis. CONCLUSION: NMO-DBr is a tool which guides professionals to take the history, record and analyze information making medical practice more consistent and improving research in the area.
OBJETIVO: Apresentar o Brazilian Neuromyelitis Optica Database System (NMO-DBr), um sistema de banco de dados que coleta, arquiva, recupera e analisa informações de pacientes com neuromielite óptica (NMO) e doenças relacionadas. MÉTODO: NMO-DBr usa o sistema Flux, um LIMS (Laboratory Information Management Systems) para gerenciamento de informações. As informações foram colhidas dos prontuários de pacientes com espectro de NMO e variantes de NMO, estas últimas definidas por quadro neurológico associado a lesões encefálicas típicas à imagem pela ressonância magnética (IRM) ou à soropositividade do anticorpo anti-aquaporina-4. RESULTADOS: NMO-DBr contém dados relativos a identificação, sintomas, condições associadas, eventos índices, recorrências, história familiar, avaliação visual e da medula, incapacidade, exames do líquor e de sangue, IRM, tomografia de coerência óptica (OCT), diagnóstico e tratamento. O sistema assegura confidencialidade, cruza dados e faz análises estatísticas. CONCLUSÃO: NMO-DBr é uma ferramenta que possibilita a prática médica mais consistente e promove a pesquisa na área.