TRANSCRIPTION OF THE TRYPANOSOMA-BRUCEI SPLICED LEADER RNA GENE IS DEPENDENT ONLY ON THE PRESENCE OF UPSTREAM REGULATORY ELEMENTS

The spliced leader (SL) RNA plays a key role in mRNA maturation in try panosomatid protozoa by providing the SL sequence, which is joined to the 5' end of every mRNA. As a first step towards a better understandi ng of the biogenesis and function of the SL RNA, we expressed a tagged SL RNA gene in a cell-free system of procyclic Trypanosoma brucei cel ls. Transcription initiates at +1 and can be detected as early as 1 mi n after addition of extract.Transcription of the SL RNA gene in vitro, as well as in permeable cells, is mediated by an alpha-amanitin/taget itoxin resistant complex, suggesting a promoter that is intermediate b etween a classical RNA polymerase II and RNA polymerase III promoter. An analysis of the promoter architecture of the SL RNA gene revealed t hat regulatory elements are located upstream of the coding region and that the SL sequence, in contrast to the nematode SL sequence, is not required for T. brucei SL RNA gene transcription. (C) 1997 Elsevier Sc ience B.V.