APE1/Ref-1 Interacts with NPM1 within Nucleoli and Plays a Role in the rRNA Quality Control Process

• DOI: 10.1128/mcb.01337-08
• Publication Date: 2009-02-03T01:58:53Z
• Authors: Carlo Vascotto; Damiano Fantini; Milena Romanello; Laura Cesaratto; Marta Deganuto; Antonio Leonardi; J. Pablo Radicella; Mark R. Kelley; Chiara D'Ambrosio; Andrea Scaloni; Franco Quadrifoglio; Gianluca Tell
• Keywords: interactome; OXIDATION; Binding, Competitive; Peptide Mapping; rRNA quality control; 03 medical and health sciences; Protein Interaction Mapping; DNA-(Apurinic or Apyrimidinic Site) Lyase; RNA, Ribosomal, 18S; Humans; Electrophoresis, Gel, Two-Dimensional; GENE-EXPRESSION; Cell Proliferation; APE1/Ref-1; 0303 health sciences; Cell Cycle; Nuclear Proteins; HUMAN AP-ENDONUCLEASE; HUMAN APURINIC/APYRIMIDINIC ENDONUCLEASE; HUMAN AP-ENDONUCLEASE; DNA-REPAIR; PROTEIN B23; ABASIC ENDONUCLEASE; ALZHEIMERS-DISEASE; GENE-EXPRESSION; EARLY EVENT; CELL-DEATH; OXIDATION; DNA; EARLY EVENT; Protein Structure, Tertiary; 3. Good health; ALZHEIMERS-DISEASE; PROTEIN B23; CELL-DEATH; RNA processing; APE1; RNA, Ribosomal; Protein Biosynthesis; ABASIC ENDONUCLEASE; DNA-REPAIR; NPM1; HUMAN APURINIC/APYRIMIDINIC ENDONUCLEASE; Protein Multimerization; Nucleophosmin; Oxidation-Reduction; Cell Nucleolus; HeLa Cells; Protein Binding

APE1/Ref-1 (hereafter, APE1), a DNA repair enzyme and a transcriptional coactivator, is a vital protein in mammals. Its role in controlling cell growth and the molecular mechanisms that fine-tune its different cellular functions are still not known. By an unbiased proteomic approach, we have identified and characterized several novel APE1 partners which, unexpectedly, include a number of proteins involved in ribosome biogenesis and RNA processing. In particular, a novel interaction between nucleophosmin (NPM1) and APE1 was characterized. We observed that the 33 N-terminal residues of APE1 are required for stable interaction with the NPM1 oligomerization domain. As a consequence of the interaction with NPM1 and RNA, APE1 is localized within the nucleolus and this localization depends on cell cycle and active rRNA transcription. NPM1 stimulates APE1 endonuclease activity on abasic double-stranded DNA (dsDNA) but decreases APE1 endonuclease activity on abasic single-stranded RNA (ssRNA) by masking the N-terminal region of APE1 required for stable RNA binding. In APE1-knocked-down cells, pre-rRNA synthesis and rRNA processing were not affected but inability to remove 8-hydroxyguanine-containing rRNA upon oxidative stress, impaired translation, lower intracellular protein content, and decreased cell growth rate were found. Our data demonstrate that APE1 affects cell growth by directly acting on RNA quality control mechanisms, thus affecting gene expression through posttranscriptional mechanisms.