Schematic representation of promoter regions in trypanosomatids. Transcription start sites are indicated by arrows. DNA sequence elements required for transcription initiation are denoted by dark blue boxes. Coding regions are shown as light blue boxes. The spliced leader RNA and chromosome 1 (transcribed by Pol II) correspond to L. tarentolae and L. major, respectively. The tRNA/U6snRNA locus and the 5S rRNA (transcribed by Pol III) correspond to T. brucei. The VSG, procyclin and rRNA transcription units (transcribed by Pol I) also correspond to T. brucei. The spliced leader RNA promoter contains the and elements [51]. In the divergent strand-switch region (SSR) from chromosome 1 several TSSs were mapped, in a ~70 bp region, for both PGCs [29]. The tRNA gene possesses boxes A and B and the U6 snRNA an initiator element (Inr) [66]. The 5S rRNA gene contains boxes A and C and an intermediate element (IE). Domains I and II regulate transcription of the VSG expression site [69]. The VSG gene is located ~47 kb downstream of the expression-site-asociated-gene 7 (ESAG7). The procyclin promoter consists of four domains (I–IV) [70]. Procyclin genes EP1 and EP2 are followed by procyclin-associated genes (PAGs) 1 and 5. The rRNA promoter contains a bipartite core element (domains I and II), a distal element (domain III) and an upstream control region (UCR) [71]. Coding regions of the 18S, 5.8S and 24S rRNA genes are shown. Maps are drawn to scale. Please note that the scales are different upstream and downstream of the TSS in the VSG, procyclin and rRNA transcription units.
