Differential regulation of ESAG transcripts in Trypanosoma brucei.

In Trypanosoma brucei, several genes termed ESAGs for expression site-associated genes are contained within the polycistronic transcription units of the VSG gene, and their transcription is coordinately regulated during the parasite life-cycle. Since the VSG mRNA is characterized by a drastic destabilization under conditions where translation is inhibited, we examined if this post-transcriptional control also applies to the ESAG mRNAs. While the ESAG 7/6 mRNA behaved like the VSG mRNA, the ESAG 8 and ESAG 3 mRNAs did not. We ascribe this differential behaviour to the residual transcription that still occurs only in the ESAG 7/6 region of the VSG unit under conditions where this unit is down-regulated.