Histone deacetylase inhibitors induce expression of chromosomally tagged variant-specific surface protein genes in Giardia lamblia

OBJECTIVE: RNA interference and miRNA mediated mechanisms have been proposed to explain the expression of a specific variant of VSP at a time on the surface of Giardia lamblia. Recently, epigenetic mechanisms involving histone acetylations have been proposed to explain the process of vsp gene switching in Giardia lamblia. However, due to the limited availability of specific antibodies for all the vsp variants present in the genome, it was difficult to monitor vsp gene switching. In this study, we have used an endogenous tagging method to tag specific vsp genes vsp1267 and vsp9B10A with a sequence encoding hemagglutinin (HA) epitope at the 3′end of the coding sequences without altering the 5′ upstream elements. With this method, we have monitored the expression of the tagged vsp genes in cells treated with histone deacetylase inhibitors using RT-PCR. RESULTS: Our results show that vsp1267-3XHA can be induced by treatment with sodium 4-phenylbutyrate, M344 and splitomicin but not by apicidin and Trichostatin A, while vsp9B10A-3XHA expression can be induced by Trichostatin A and splitomicin but not by sodium 4-phenylbutyrate, M344 and apicidin. The induced expression of these variants was not due to growth inhibition. These results support the role of histone acetylations in vsp expression.