Cleavage of the Saccharomyces cerevisiae primary ribosomal RNA (rRNA) transcript in the 3′ external transcribed spacer (ETS) by Rnt1p generates the 35S pre-rRNA, the earliest detectable species in the pre-rRNA processing pathway. In this study we show that Rnt1p is concentrated in a subnucleolar dot-shaped territory distinct from the nucleolar body. The 35S pre-rRNA is localized at the periphery of the Rnt1p dot, in a pattern that suggests a diffusion of the 35S pre-rRNA from the site of Rnt1p processing. When plasmid-borne versions of the rDNA are used to express rRNAs, the Rnt1p territory reorganizes around these plasmids, suggesting a close association between Rnt1p and the plasmid-borne rDNA units. Rnt1p was found associated with the endogenous rDNA by chromatin immunoprecipitation. Deletion of functionally important Rnt1p domains result in a loss of the dot-shaped territory, showing that this subnucleolar territory corresponds to a functional site of processing. These results show that a large fraction of Rnt1p is localized at the site of transcription of the rDNA, suggesting that the cleavage of the primary pre-rRNA transcript to generate the 35S pre-rRNA is a cotranscriptional event.
A cotranscriptional model for 3 ‘-end processing of the Saccharomyces cerevisiae pre-ribosomal RNA precursor
Henras, A. K.; Bertrand, E.; Chanfreau, G.
Rna-a Publication of the Rna Society
2004-10 / vol 10 / pages 1572-1585
transcription; protein; cell-cycle; nuclear import; localization; nucleolus; small nucleolar rnas; budding yeast; binding domain; endonuclease; polymerase-i; rnase iii; rnt1p; structural basis