Chromatin Structure in Trypanosomatids

BEATI MARÍA PAULA; OCAMPO JOSEFINA; ALONSO GUILLERMO D.; MASSIMINO STEPNICKA MILENA

Mar del Plata

Congreso; ANNUAL MEETING OF BIOSCIENCE SOCIETIES 2019, XXXI Annual Meeting of Sociedad Argentina de Protozoología (SAP); 2019

With the advent of genome wide studies important progress has been made in our understanding of the role of chromatin organization in gene regulation from yeast to human. Chromatin structure is affected in many human developmental diseases and cancers. Moreover, it regulates pathogenesis in eukaryotic microorganisms. Most of our knowledge comes from the budding yeast Saccharomyces cerevisiae. In yeast, nucleosomes are regularly spaced and phased relative to the transcription start site (TSS) and there is a nucleosome depleted region (NDR) at promoter regions. In higher eukaryotes, this precise chromatin organization is only evident for actively transcribed genes. Nevertheless, for early branching eukaryotes such as Trypanosome cruzi, chromatin organization remains poorly understood. Nucleosomes maps has been generated for the procyclic and bloodstream forms of Trypanosome brucei. No evident changes had been noticed between life forms, but they differ substantially from other eukaryotes. A unique feature for Trypanosomes is that genes transcribed by RNA pol II are organized in long poly-transcription units. Unlike yeast genome, nucleosome positioning is not well defined and there is a NDR not only at TSSs, but also upstream of every gene, coincidental with splicing acceptor site. This observation correlates with RNA pol II recruitment suggesting a role for nucleosomes during RNA maturation more than with transcription initiation. We have recently mapped nucleosomes in T. cruzi epimastigotes for CL- Brener and Sylvio strains. To make a comprehensive analysis we need to correlate our results with transcriptomic and epigenetic marks. Unfortunatelly, only a few genomic studies are available, and they have been performed in different T. cruzi strains. Nevertheless, we could corroborate that as it was described for T. brucei, in T. cruzi epimastigotes there is a mild nucleosome trough at the first ATG of each gene and a more pronounced one at splicing acceptor sites.