rRNA transcription is integral to liquid-liquid phase separation and maintenance of nucleolar structure

Beginning with transcription of ribosomal RNA (rRNA) by RNA Polymerase (Pol) I in the nucleolus, ribosome biogenesis is intimately tied to cell growth and proliferation. Perturbation of ribosome biogenesis has been previously shown to affect nucleolar structure, yet the underlying mechanism is unkno...

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Bibliographic Details
Published inbioRxiv
Main Authors Dash, Soma, Lamb, Maureen C, Lange, Jeffrey J, Mckinney, Mary Cathleen, Tsuchiya, Dai, Guo, Fengli, Zhao, Xia, Corbin, Timothy J, Kirkman, Maryellen, Delventhal, Kym, Moore, Emma L, Mckinney, Sean A, Shiang, Rita, Trainor, Paul
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 15.11.2022
Subjects
Biosynthesis
DNA-directed RNA polymerase
Embryos
Mutants
Nucleoli
Phenotypes
RNA polymerase
rRNA
Transcription
Yeast
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Summary:Beginning with transcription of ribosomal RNA (rRNA) by RNA Polymerase (Pol) I in the nucleolus, ribosome biogenesis is intimately tied to cell growth and proliferation. Perturbation of ribosome biogenesis has been previously shown to affect nucleolar structure, yet the underlying mechanism is unknown. We generated loss-of-function mouse mutants of Pol I subunits, Polr1a, Polr1b, Polr1c and Polr1d, thereby genetically inhibiting rRNA transcription and ribosome biogenesis. Pol I mutant embryos are preimplantation lethal and have fewer nucleoli. Using hiPSCs triple labeled for the three nucleolar compartments, we observe two phenotypes upon Pol I inhibition: a single condensed nucleolus, and fragmented nucleoli. We find that when rRNA transcription is inhibited, the viscosity of the granular compartment of the nucleolus is increased disrupting its liquid-liquid phase separation properties, which results in a condensed nucleolus. Taken together, our data suggests that Pol I function and rRNA transcription are required for maintaining nucleolar structure and integrity.Competing Interest StatementThe authors have declared no competing interest.
DOI:10.1101/2022.11.14.516489