HISTONE POST-TRANSLATIONAL MODIFICATIONS IN THE PROTOZOAN PARASITE GIARDIA LAMBLIA

AGOSTINA SALUSSO; JAQUET SPENCER; DIAZ PEREZ LUCIANO; PAWEL CIBOROWSKI; ROPOLO ANDREA

Congreso; LV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2019

Histones are very low molecular weight proteins that together with DNA create chromatin in eukaryotic cells. The amino terminal ends of histones are susceptible to post-translational modifications, which have an impact on chromatin structure and therefore on the regulation of gene expression. At present, it is proposed that all of these modifications on histone tails form an undercover language known as the "histone code", which is read by different proteins, to give rise to subsequent events. In the protozoan parasite Giardia lamblia, epigenetic modifications have begun to be studied in recent years, analyzing histone modifying enzymes, but so far, the particular modifications of each histone are unknown. The main objective of this work is to obtain the complete map of the post-translational modifications in the histones of Giardia lamblia. To do this, we isolate the histones of growing trophozoites and perform mass spectrometry tests using two liquid chromatography and mass spectrometry platforms. We identify different peptides of H2A, H2B, H3 and H4 included in the Giardia histone code. We found modifications preserved in other organisms, such as lysine acetylation, lysine and arginine methylation, threonine and tyrosine phosphorylation and lysine ubiquitination. In turn, we describe for the first time the propionylation of amino acids in Giardia trophozoites. We observe that the same amino acid can suffer different types of modifications at same time and depending on the type of that modification, different modifications may appear in close residues, which would indicate that there is an exchange of information (cross talk) between the histones of Giardia lamblia. Respect to arginine methylation, there are no enzymes described as HRMT (histone-arginine methyltransferase) in Giardia genome, but there are three enzymes present as possible histone methyltransferases, HMT1, HMT2 and SET2 described as HKMT (histone lysine methyltransferases), so the presence of methylated arginines indicates that possibly some of the HMTs that modify lysines, could also be modifying arginines. We study the role of HMT1 and HMT2 during growth and encystation of Giardia lamblia, and we observed that both have an implication in the encystation process. Finally, our work provides the first large-scale characterization of the Giardia histone code, which constitutes a platform for the development of future research in the field of epigenetic in this parasite.