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TP53INP2/DOR, a mediator of cell autophagy, promotes rDNA transcription via facilitating the assembly of the POLR1/RNA polymerase I preinitiation complex at rDNA promoters

ABSTRACT Cells control their metabolism through modulating the anabolic and catabolic pathways. TP53INP2/DOR (tumor protein p53 inducible nuclear protein 2), participates in cell catabolism by serving as a promoter of autophagy. Here we uncover a novel function of TP53INP2 in protein synthesis, a major biosynthetic and energy-consuming anabolic process. TP53INP2 localizes to the nucleolus through its nucleolar localization signal (NoLS) located at the C-terminal domain. Chromatin immunoprecipitation (ChIP) assays detected an association of TP53INP2 with the ribosomal DNA (rDNA), when exclusion of TP53INP2 from the nucleolus repressed rDNA promoter activity and the production of ribosomal RNA (rRNA) and proteins. The removal of TP53INP2 also impaired the association of the POLR1/RNA polymerase I preinitiation complex (PIC) with rDNA. Further, TP53INP2 interacts directly with POLR1 PIC, and is required for the assembly of the complex. These data indicate that TP53INP2 promotes ribosome biogenesis through facilitating rRNA synthesis at the nucleolus, suggesting a dual role of TP53INP2 in cell metabolism, assisting anabolism on the nucleolus, and stimulating catabolism off the nucleolus.