Bidirectional silencing of RNA polymerase I transcription by a strand switch region in Trypanosoma brucei

摘要: The procyclin genes in Trypanosoma brucei are transcribed by RNA polymerase I as part of 5-10 kb long polycistronic transcription units on chromosomes VI and X. Each locus begins with two followed at least one procyclin-associated gene (PAG). In procyclic (insect midgut) form trypanosomes, PAG mRNA levels about 100-fold lower than those procyclins. We show that deletion PAG1, PAG2 or PAG3 results increased from downstream the same unit. Nascent analysis revealed most effects due to elongation knockouts. Furthermore, transient stable transfections showed sequence elements both strands PAG1 can inhibit Pol transcription. Finally, database mining we identified 30 additional PAG-related sequences located almost exclusively strand switch regions and/or sites where a change type is likely occur.