385_PUTATIVE QUADRUPLEX SEQUENCE (PQS) DISRTRIBUTION IN TRYPANOSOMATID GENOMES: A MARK FOR TRANSCRIPTION OR TRANSLATION TERMINATION?

MARGARIT, EZEQUIEL; ANDINO, DIEGO ; CRIBB, PAMELA

BUENOS AIRES

Congreso; Reunion Conjunta de Sociedades de Biociencias 2017; 2017

REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS

385_PUTATIVE QUADRUPLEX SEQUENCE (PQS) DISRTRIBUTION IN TRYPANOSOMATID GENOMES: A MARK FOR TRANSCRIPTION OR TRANSLATION TERMINATION?Trypanosomatids cause important diseases in humans like Leishmaniosis andChagas disease. Their genes present an unusual organization in polycistronictranscription units (PTUs) that are transcribed together from a strand switchregion (SSR) without canonical promoters. Polycistronic transcripts areprocessed by trans-splicing and polyadenylation to give mature mRNAs.Trypanosomatids do not rely on typical transcriptional mechanisms to controlgene expression. Instead, various post-transcriptional events seem to modulatethe final protein content. More recently, epigenetic marks and chromatin statehave shown to be important actors in control of gene expression.Guanine Quadruplexes (G4) are secondary structures formed in DNA or RNAregions rich in guanines. G4 have been implicated in transcriptional regulationand in recombination of immunologlobin and antigenic variation-related genesin several pathogenic organisms.We performed a bioinformatic analysis of the frequency and distribution ofputative guanine quadruplexes (PQSs) in the genomes of Leishmania andTrypanosoma species in order to evaluate their possible impact on the controlof gene expression at transcriptional and post-transcriptional levels.In Leishmania, we observed a higher density of PQSs (concordant with thehigher GC content in this genus) compared with Trypanosoma species. PQSsare enriched in the terminal end of the PTUs of the template strand, adjacent toconvergent SSRs. This pattern suggests a possible relationship between G4sand transcription termination in Leishmania. No clear correlation between PQSdistribution and possible functions was found in Trypanosoma genomes. Then,we analyzed PQSs distribution inside the PTUs of both genera. An outstandingdifference was observed between genes and intergenic sequences, with a verylow density of PQSs in coding-sequences in relation to intergenic regions, whatmay suggest a putative role of G4s in RNA maturation, stability and/ortranslation.