Putative quadruplex sequence (pqs) disrtribution in trypanosomatid genomes: a mark for transcription or translation termination?

MARGARIT, E.; ANDINO, D.; CRIBB, P.

Capital Federal

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

PUTATIVE QUADRUPLEX SEQUENCE (PQS) DISRTRIBUTIONIN TRYPANOSOMATID GENOMES: A MARKFOR TRANSCRIPTION OR TRANSLATION TERMINATION?Diego Andino (1), Ezequiel Margarit (2), Pamela Cribb (3)(1) UNLAR. (2) CEFOBI-CONICET-UNR. (3) IBR-CONICETUNR.Trypanosomatids cause important diseases in humans like Leishmaniosisand Chagas disease. Their genes present an unusual organizationin polycistronic transcription units (PTUs) that are transcribedtogether from a strand switch region (SSR) without canonicalpromoters. Polycistronic transcripts are processed by trans-splicingand polyadenylation to give mature mRNAs.Trypanosomatids do not rely on typical transcriptional mechanismsto control gene expression. Instead, various post-transcriptionalevents seem to modulate the final protein content. More recently,epigenetic marks and chromatin state have shown to be importantactors in control of gene expression.Guanine Quadruplexes (G4) are secondary structures formed inDNA or RNA regions rich in guanines. G4 have been implicated intranscriptional regulation and in recombination of immunologlobinand antigenic variation-related genes in several pathogenic organisms.We performed a bioinformatic analysis of the frequency and distributionof putative guanine quadruplexes (PQSs) in the genomesof Leishmania and Trypanosoma species in order to evaluate theirpossible impact on the control of gene expression at transcriptionaland post-transcriptional levels.In Leishmania, we observed a higher density of PQSs (concordantwith the higher GC content in this genus) compared with Trypanosomaspecies. PQSs are enriched in the terminal end of the PTUs ofthe template strand, adjacent to convergent SSRs. This pattern suggestsa possible relationship between G4s and transcription terminationin Leishmania. No clear correlation between PQS distributionand possible functions was found in Trypanosoma genomes. Then,we analyzed PQSs distribution inside the PTUs of both genera. Anoutstanding difference was observed between genes and intergenicsequences, with a very low density of PQSs in coding-sequences inrelation to intergenic regions, what may suggest a putative role ofG4s in RNA maturation, stability and/or translation.