Unusual diversity in alpha-amanitin sensitivity of RNA polymerases in trichomonads

Previous studies in the parasitic protist Trichomonas vaginalis have reveal ed that protein coding genes are transcribed by an alpha -amanitin-resistan t RNA polymerase (RNAP) II. To investigate whether this unusual property is a general characteristic of trichomonads, we addressed the physiology of R NA synthesis in lysolecithin-permeabilized cells. Unlike in T. vaginalis. R NAP II in Tritrichomonas foetus was highly sensitive to the inhibitor alpha -amanitin. On the other hand, RNAP III, identified by its sensitivity to t he specific inhibitor tagetitoxin, was found to be resistant to alpha -aman itin in Tritrichomonas foetus, but showed a typical intermediate sensitivit y in T. vaginalis. Extension of this study to an additional seven trichomon ad species confirmed this genera specific pattern of alpha -amanitin sensit ivity and highlighted an unusual diversity in RNAPs among trichomonads, a c losely related group of unicellular eukaryotes. (C) 2001 Elsevier Science B .V. All rights reserved.