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. 2007 Feb 8;7(Suppl 1):S13. doi: 10.1186/1471-2148-7-S1-S13

Figure 4.

Figure 4

Promoter regions of Human MRP, P and U6.A. Organization of pre-rRNA based on [37]. In bacteria rRNA genes are co-transcribed as a polycistronic precursor (although exceptions are common). Most eukaryotes vary only in the length of their ITS regions, an extreme case being the microsporidian Encephalitozoon cuniculi which has completely lost its ITS2 having a fused 5.8S/28S subunit. RNase P and RNase MRP do not cleave the main transcripts but trim the ends of their respective substrates (the tRNA or 5.8S rRNA) after cleavage by other enzymes. In eukaryotes the 5S rRNA is transcribed separately by RNA polymerase III. B. The Diplomonad Giardia lamblia has the usual order of rRNA subunits with short ITS regions, however RNase MRP has not yet been characterized from this species. RNAstructure folding of G. lamblia ITS1 [56] showing a single stranded region between two stem loops that could possibly be an A3 site. Other foldings of this sequence and foldings of other sequences (DQ157272 and AF239841) produce just a single stem-loop.