title: Structure analysis of FAAP24 reveals single-stranded DNA-binding activity and domain functions in DNA damage response.
abstract: The FANCM/FAAP24 heterodimer has distinct functions in protecting cells from complex DNA lesions such as interstrand crosslinks. These functions rely on the biochemical activity of FANCM/FAAP24 to recognize and bind to damaged DNA or stalled replication forks. However, the DNA-binding activity of this complex was not clearly defined. We investigated how FAAP24 contributes to the DNA-interacting functions of the FANCM/FAAP24 complex by acquiring the N-terminal and C-terminal solution structures of human FAAP24. Modeling of the FAAP24 structure indicates that FAAP24 may possess a high affinity toward single-stranded DNA (ssDNA). Testing of various FAAP24 mutations in vitro and in vivo validated this prediction derived from structural analyses. We found that the DNA-binding and FANCM-interacting functions of FAAP24, although both require the C-terminal (HhH)2 domain, can be distinguished by segregation-of-function mutations. These results demonstrate dual roles of FAAP24 in DNA damage response against crosslinking lesions, one through the formation of FANCM/FAAP24 heterodimer and the other via its ssDNA-binding activity required in optimized checkpoint activation.
authors.affiliation: Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Yucai
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiao
authors.initials: X
authors.lastname: Han
authors.forename: Fangming
authors.initials: F
authors.lastname: Wu
authors.forename: Justin W
authors.initials: JW
authors.lastname: Leung
authors.forename: Megan G
authors.initials: MG
authors.lastname: Lowery
authors.forename: Huong
authors.initials: H
authors.lastname: Do
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
authors.forename: Chaowei
authors.initials: C
authors.lastname: Shi
authors.forename: Changlin
authors.initials: C
authors.lastname: Tian
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Weimin
authors.initials: W
authors.lastname: Gong
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D051856:Fanconi Anemia Complementation Group Proteins; D006801:Humans; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
chemical_list: D002843:Chromatin; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C518296:FAAP24 protein, human; D051856:Fanconi Anemia Complementation Group Proteins; D000255:Adenosine Triphosphate; C518295:FANCM protein, human; D004265:DNA Helicases