Histone methyl-transferase 1 is a key regulator of the encystation process in the parasite Giardia lamblia

SALUSSO, AGOSTINA; ZAMPONI, NAHUEL; MAYOL, GONZALO; ZLOCOWSKI, NATACHA; RÓPOLO AS

Havana

Congreso; 6th. International Giardia and Cryptosporidium Conference; 2017

In eukaryotes, histone lysine methylation is associated with either 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 GlHMT1 overexpression or downregulation, we observed an increase or a decrease of cyst production respectively, compared to wild-type trophozoites. A time-lapse analysis of encystation showed that overexpression of GlHMT1 induced an earlier and faster process than in wild-type cells together with an upregulation of mRNA expression of cyst wall proteins. Subcellular localization studies indicated that GlHMT1-HA was mainly associated with the nuclear and perinuclear region in both growing and encysting parasites, in agreement with bioinformatics analyses showing that GlHMT-1 possesses nuclear localization signals in addition to the classical SET and post-SET domains. 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.