The Entamoeba histolytica methylated LINE-binding protein EhMLBP provides protection against heat shock.

Adaptation to environmental stress is a key process that allows the unicellular parasite Entamoeba histolytica to survive in its human host. We previously characterized EhMLBP as an essential protein for the growth and the virulence of the parasite. EhMLBP binds to methylated repetitive DNA, and is one of the core proteins of the parasite's epigenetic machinery. Here, we show that EhMLBP and heat shock proteins have common properties. EhMLBP is induced by heat shock and its expression is regulated by a heat shock element binding site that is located in its 5' non-coding region. Following heat shock, the perinuclear localization of EhMLBP in control trophozoites is replaced by an even distribution within the nucleus alongside with an enhanced recruitment of EhMLBP to the reverse transcriptase of a long interspersed nucleotide element (LINE) DNA. Constitutive overexpression of EhMLBP protects trophozoites against heat shock and reduces protein aggregation. This protective function is lost in trophozoites that overexpress a mutated form of EhMLBP which is devoid of its heat shock domain. To the best of our knowledge, this is the first report of a methyl DNA-binding protein that plays a protective role against heat shock.