Padrões de poliadenilação em moléculas de RNAs de Leishmania obtidas da análise de transcriptoma

• Autor(a) principal: Santos, Ramon de Freitas
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/323
• topic: Poliadenilação; Leismania; Transcriptoma; Polyadenylation; Leishmania; Transcriptome; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::BIOLOGIA MOLECULAR

The high throughput next generation sequencing (NGS) has revealed new aspects on genomes and transcriptomes that was not observed or poor described using small scale sequencing. Using two species of Leishmania as a model in a typical transcriptome analysis and the NGS 454 pirosequencing we found non canonical polyadenilations at rRNAs and mRNAs. Leishmania´s RNAs, including rRNAs are transcribed as polycistronical long pre-rRNAs, but usually only mRNAs are processed by poly(A)+ polymerases that add canonical 3´-poly(A)+ tails. Analyzing the transcriptome data we observed poly(A)+ rich tails at the end of rRNA subunits too. This phenomenon could be direct related with the common high rRNA contaminants observed in general mRNA samples after purification by oligo(dT) affinity approach. Surprisingly we found many poly(A)+ rich tails at 3´-end at the middle of the predicted transcripts (both rRNA and mRNA) interrupting the message and probably related to a new post-transcriptional control of gene expression in Leishmania. We proved these founds by conventional RT-PCR and sangerSanger sequencing using 28S beta rRNA, 18S rRNA, as rRNA targets and 60S ribosomal protein L5 and eiF5a2 mRNA targets. The internal poly(A)+-rich tailed RNA truncation phenomenon open new fields on post-transcriptional gene expression regulation in Leishmania and related organisms. It adds further complexity to the paradigm that almost the entire trypanosomatids genomes are constitutively expressed, in that the integrity of messages could play an important role in regulating the pool of genes that are effectively translated. These data highlight the importance to evaluate this RNA modification in high throughput transcriptome analyses opening new fields on the studies of transcriptome in general and trypanosomatids gene expression and transcripts stabilities in particular.