title: A novel role for Gadd45α in base excision repair: modulation of APE1 activity by the direct interaction of Gadd45α with PCNA.
abstract: The growth arrest and DNA damage inducible, alpha (Gadd45α) protein regulates DNA repair by interacting with proliferating cell nuclear antigen (PCNA). Our previous study suggested a potential role for Gadd45α in the base excision repair (BER) pathway by affecting apurinic/apyrimidinic endonuclease 1 (APE1) protein in addition to its accepted role in nucleotide excision repair (NER). Here, we investigated whether the interaction of Gadd45α with PCNA affects APE1 activity. To address this issue, we used a siRNA directed to Gadd45α and a form of Gadd45α with a mutation to the predicted site of PCNA binding. There was a reduction of APE1 activity in cells transfected with the Gadd45α siRNA. Furthermore, the interaction of Gadd45α with PCNA and APE1 was lower in cells transfected with mutant Gadd45α compared with cells transfected with wild-type Gadd45α. Indeed, we observed that the APE1 activity in the Gadd45α-interacting complex was significantly lower in cells that overexpress mutant Gadd45α compared with cells that overexpress wild-type Gadd45α. We conclude that the PCNA binding site on Gadd45α plays a critical role in modulating the interaction with PCNA and APE1, affecting BER activity. These results provide novel insights into the mechanisms by which BER activity is modulated, although the interaction of Gadd45α with APE1 needs to be clarified.
authors.affiliation: Department of Life Science, Dongguk University, 30 Pildong-ro 1-gil, Jung-gu, Seoul 100-715, Republic of Korea.
authors.forename: Hye Lim
authors.initials: HL
authors.lastname: Kim
authors.forename: Sang Uk
authors.initials: SU
authors.lastname: Kim
authors.forename: Young Rok
authors.initials: YR
authors.lastname: Seo
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D057075:Enzyme Assays; D056945:Hep G2 Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D034741:RNA, Small Interfering; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C085108:APEX1 protein, human