UNRAVELLING THE FUNCTION OF THE UNIQUE N-TERMINAL DOMAIN OF TRYPANOSOMA CRUZI HIGH MOBILITY GROUP B PROTEIN.

TAVERNELLI LUIS; ALONSO VICTORIA LUCÍA; PEZZA ALEJANDRO; SERRA ESTEBAN; CRIBB PAMELA

Buenos Aires.

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SAP

High Mobility Group B (HMGBs) are a family of chromatin proteinscapable of binding non-canonical DNA structures through oneor more ?HMG box? domains. These proteins are highly conservedamong eukaryotic organisms and are involved in key nuclear processeslike transcription, replication, recombination and DNA repair.The HMGB from Trypanosoma cruzi (TcHMGB) contains two ?HMGbox? domains and a unique N-terminal sequence present only intrypanosomatids? HMGBs. In silico studies showed that within thisregion there is a nuclear localization signal (NLS) and a DEK-Cterminal domain, a putative third DNA-binding domain in trypanosomes´ HMGBs.We obtained parasites capable of overexpressing truncated formsof TcHMGB (N-terminal domain and TcHMGBΔN) and the full lengthTcHMGB as well. Immunofluorescence assays showed that the wildtype version is located in the nucleus but when we overexpressedTcHMGB lacking the N terminal domain (TcHMGBΔN) the proteinis distributed along the whole parasite but excluded from the nucleus.On the other hand, when we overexpressed only the N-terminalregion, this fragment accumulated in the nucleus but also it wasdetected in the cytoplasm. These results suggest that the NLS isnecessary but not sufficient to drive the protein to the nucleus.We previously determined that overexpression of TcHMGB resultsin changes in chromatin structure that is detrimental for the parasitefitness. We now evaluated the effect of overexpressing the N-terminal region alone, which caused a dramatic decrease in epimastigotesgrowth. In order to clarify this phenotype we analyzed the cellcycle by flow cytometry with synchronized cultures in the G1 phase,showing a clear delay in the cell progression compared to the negativecontrol. In vitro infection assays showed that amastigotes replicationcan also be affected. We propose that the DEK-C terminaldomain may be another contact point of TcHMGB with nuclear DNAcontributing to chromatin structure remodeling.