Mono-allelic VSG expression by RNA polymerase I in Trypanosoma brucei: expression site control from both ends?

摘要: Abstract Trypanosoma brucei is a vector borne, lethal protistan parasite of humans and livestock in sub-Saharan Africa. Antigenic variation its cell surface coat enables the to evade adaptive immune responses live freely blood mammalian hosts. The consists ten million copies variant glycoprotein (VSG) that expressed from single VSG gene, drawn large repertoire located near telomere at one fifteen so-called bloodstream expression sites (BESs). Thus, antigenic achieved by switching different gene. A BES tandem array site-associated genes terminal It polycistronically transcribed multifunctional RNA polymerase I (RNAPI) short promoter 45–60 kb upstream mechanism(s) restricting are not well understood. There convincing evidence epigenetic silencing transcription attenuation play important roles. Furthermore, recent data indicated there regulation level initiation that, surprisingly, mRNA appears have role Here, we review propose model which telomere-directed, opposed promoter-directed, activated RNAPI transcription.