title: RNAP-II transcribes two small RNAs at the promoter and terminator regions of the RNAP-I gene in Saccharomyces cerevisiae.
abstract: Three RNA polymerases coexist in the ribosomal DNA of Saccharomyces cerevisiae. RNAP-I transcribes the 35S rRNA, RNAP-III transcribes the 5S rRNA and RNAP-II is found in both intergenic non-coding regions. Previously, we demonstrated that RNAP-II molecules bound to the intergenic non-coding regions (IGS) of the ribosomal locus are mainly found in a stalled conformation, and the stalled polymerase mediates chromatin interactions, which isolate RNAP-I from the RNAP-III transcriptional domain. Besides, RNAP-II transcribes both IGS regions at low levels, using different cryptic promoters. This report demonstrates that RNAP-II also transcribes two sequences located in the 5'- and 3'-ends of the 35S rRNA gene that overlap with the sequences of the 35S rRNA precursor transcribed by RNAP-I. The sequence located at the promoter region of RNAP-I, called the p-RNA transcript, binds to the transcription termination-related protein, Reb1p, while the T-RNA sequence, located in the termination sites of RNAP-I gene, contains the stem-loop recognized by Rtn1p, which is necessary for proper termination of RNAP-I. Because of their location, these small RNAs may play a key role in the initiation and termination of RNAP-I transcription. To correctly synthesize proteins, eukaryotic cells may retain a mechanism that connects the three main polymerases. This report suggests that cryptic transcription by RNAP-II may be required for normal transcription by RNAP-I in the ribosomal locus of S. cerevisiae.
authors.affiliation: MRC Clinical Sciences Centre, Imperial College, London, UK. m.mayan@csc.mrc.ac.uk
authors.forename: Maria D
authors.initials: MD
authors.lastname: Mayán
mesh_terms: D015966:Gene Expression Regulation, Fungal; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics*; D012318:RNA Polymerase I / Q000235:genetics*; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D012313:RNA; D012319:RNA Polymerase II; D012318:RNA Polymerase I