title: Selective inhibition of rRNA transcription downregulates E2F-1: a new p53-independent mechanism linking cell growth to cell proliferation.
abstract: The tumour suppressor p53 negatively controls cell cycle progression in response to perturbed ribosome biogenesis in mammalian cells, thus coordinating growth with proliferation. Unlike mammalian cells, p53 is not involved in the growth control of proliferation in yeasts and flies. We investigated whether a p53-independent mechanism of response to inadequate ribosome biogenesis rate is also present in mammalian cells. We studied the effect of specific inhibition of rRNA synthesis on cell cycle progression in human cancer cell lines using the small-interfering RNA procedure to silence the POLR1A gene, which encodes the catalytic subunit of RNA polymerase I. We found that interference of POLR1A inhibited the synthesis of rRNA and hindered cell cycle progression in cells with inactivated p53, as a consequence of downregulation of the transcription factor E2F-1. Downregulation of E2F-1 was due to release of the ribosomal protein L11, which inactivated the E2F-1-stabilising function of the E3 ubiquitin protein ligase MDM2. These results demonstrated the existence of a p53-independent mechanism that links cell growth to cell proliferation in mammalian cells, and suggested that selective targeting of the RNA polymerase I transcription machinery might be advisable to hinder proliferation of p53-deficient cancer cells.
authors: Dipartimento di Patologia Sperimentale, Università di Bologna, 40126 Bologna, Italy.
authors: Giulio
authors: G
authors: Donati
authors: Elisa
authors: E
authors: Brighenti
authors: Manuela
authors: M
authors: Vici
authors: Giuliano
authors: G
authors: Mazzini
authors: Davide
authors: D
authors: Treré
authors: Lorenzo
authors: L
authors: Montanaro
authors: Massimo
authors: M
authors: Derenzini
mesh_terms: D020134:Catalytic Domain; D002453:Cell Cycle / Q000235:genetics; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D015536:Down-Regulation; D050687:E2F1 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D045325:HCT116 Cells; D006801:Humans; D012318:RNA Polymerase I / Q000235:genetics*; D012335:RNA, Ribosomal / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D012335:RNA, Ribosomal; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D012318:RNA Polymerase I