title: Quaternary structure of ATR and effects of ATRIP and replication protein A on its DNA binding and kinase activities.
abstract: ATR is an essential protein that functions as a damage sensor and a proximal kinase in the DNA damage checkpoint response in mammalian cells. It is a member of the phosphoinositide 3-kinase-like kinase (PIKK) family, which includes ATM, ATR, and DNA-dependent protein kinase. Recently, it was found that ATM is an oligomeric protein that is converted to an active monomeric form by phosphorylation in trans upon DNA damage, and this raised the possibility that other members of the PIKK family may be regulated in a similar manner. Here we show that ATR is a monomeric protein associated with a smaller protein called ATRIP with moderate affinity. The ATR protein by itself or in the form of the ATR-ATRIP heterodimer binds to naked or replication protein A (RPA)-covered DNAs with comparable affinities. However, the phosphorylation of RPA by ATR is dependent on single-stranded DNA and is stimulated by ATRIP. These findings suggest that the regulation and mechanism of action of ATR are fundamentally different from those of the other PIKK proteins.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: Keziban
authors.initials: K
authors.lastname: Unsal-Kaçmaz
authors.forename: Aziz
authors.initials: A
authors.lastname: Sancar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000528:radiation effects; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005090:Exodeoxyribonucleases; D006801:Humans; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D020836:Protein Structure, Quaternary; D051716:Replication Protein A; D014466:Ultraviolet Rays
chemical_list: C521194:ATRIP protein, human; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D010750:Phosphoproteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D004247:DNA; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D005090:Exodeoxyribonucleases; C429526:three prime repair exonuclease 1