Unique Aspects of rRNA Biogenesis in Trypanosomatids.

Trypanosomatids are protozoan parasites that cycle between an insect and a mammalian host. The large-subunit rRNA of these organisms undergoes unique processing events absent in other eukaryotes. Recently, small nucleolar RNAs (snoRNAs) that mediate these specific cleavages were identified. Trypanosomatid rRNA is rich in RNA modifications such as 2'-O-methylation (Nm) and pseudouridylation (Ψ) that are also guided by these snoRNAs. A subset of these modifications is developmentally regulated and increased in the parasite form that propagates in the mammalian host. Such hypermodification contributes the temperature adaptation and hence infectivity during cycling of the parasite. rRNA processing and modification should be considered promising drug targets for fighting the diseases caused by these parasites.