The SLA RNA gene of Trypanosoma brucei is organized in a tandem array which encodes several small RNAs

We have recently identified the Spliced Leader Associated RNA (SLA RNA) which is implicated in pre-messenger RNA splicing in Trypanosoma brucei by virtue of its interaction with the 5' splice site of the trans spliced spliced leader RNA (SL RNA) in vivo. Southern analyses reveal that the SLA RNA gene is found in a tandem array of 10-11 copies per haploid genome in T. brucei. Each repeat unit in the array encodes three additional small RNAs of unknown function. RNA polymerase inhibition studies are consistent with transcription of all four genes by the same polymerase, but do not clearly differentiate between RNA polymerases II and III. The SLA RNA has homologs in other kinetoplastid protozoa and we have determined the sequence from two additional species. Trypanosoma cruzi and Crithidia fasciculata. Features of both secondary structure and sequence are conserved in these organisms. One conserved element, 5'-UGUAGUG-3', has the potential to base-pair to the SL RNA upstream of the 5' splice site. This potential interaction is consistent with the sites of SL RNA to SLA RNA psoralen cross-linking in vivo [1].