Involvement of histone methyltransferase-1 in Giardia lamblia differentiation

AGOSTINA SALUSSO; ANDREA SILVANA ROPOLO; NATACHA ZLOCOWSKI; NAHUEL ZAMPONI; GONZALO MAYOL

Cordoba

Congreso; LII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

In eukaryotes, histone lysine methylation is associated either with active or repressed chromatin states, depending on the status of methylation. Even when the amino-terminus of Giardia lamblia histones diverges from other organisms, these regions contain lysine residues that are potential targets for methylation. When we examined the role of the histone methyltransferase 1 (HMT1) in the regulation of the encystation process by HMT1 overexpression or downregulation in transfected trophozoites, we observed an increase or decrease of cyst production, respectively, compared with wild-type trophozoites. Time-lapse analysis of encystation showed that overexpression of HMT1-HA induced an earlier and faster process than in wild-type cells together with an up-regulation of the mRNA expression of cyst wall proteins. Localization studies indicated that HMT1-HA was mainly associated with the nuclear and perinuclear region during growth and encystation of the parasite, in agreement with bioinformatic analysis showing that HMT-1 of Giardia possesses nuclear localization signals in addition to the classical SET- and post-SET domain. Altogether, these findings suggest that the function of HMT1 is critical for the success and timing of the encystation process and reinforce the idea that epigenetic marks are critical for cyst formation in G. lamblia.