Browsing by Author "Deganuto, Marta"

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    APE1/Ref-1 Interacts with NPM1 within Nucleoli and Plays a Role in the rRNA Quality Control Process
    (2009-04) Vascotto, Carlo; Fantini, Damiano; Romanello, Milena; Cesaratto, Laura; Deganuto, Marta; Leonardi, Antonio; Radicella, J Pablo; Kelley, Mark R.; D'Ambrosio, Chiara; Scaloni, Andrea; Quadrifoglio, Franco; Tell, Gianluca
    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.
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    Genome-wide analysis and proteomic studies reveal APE1/Ref-1 multifunctional role in mammalian cells
    (2009-02) Vascotto, Carlo; Cesaratto, Laura; Zeef, Leo AH.; Deganuto, Marta; D'Ambrosio, Chiara; Scaloni, Andrea; Romanello, Milena; Damante, Giuseppe; Taglialatela, Giulio; Delneri, Daniela; Kelley, Mark R.; Mitra, Sankar; Quadrifoglio, Franco; Tell, Gianluca
    Apurinic apyrimidinic endonuclease/redox effector factor 1 (APE1/Ref-1) protects cells from oxidative stress by acting as a central enzyme in base excision repair pathways of DNA lesions and through its independent activity as a redox transcriptional co-activator. Dysregulation of this protein has been associated with cancer development. At present, contrasting data have been published regarding the biological relevance of the two functions as well as the molecular mechanisms involved. Here, we combined both mRNA expression profiling and proteomic analysis to determine the molecular changes associated with APE1 loss-of-expression induced by siRNA technology. This approach identified a role of APE1 in cell growth, apoptosis, intracellular redox state, mitochondrial function, and cytoskeletal structure. Overall, our data show that APE1 acts as a hub in coordinating different and vital functions in mammalian cells, highlighting the molecular determinants of the multifunctional nature of APE1 protein.