A minimal threshold of FANCJ helicase activity is required for its response to replication stress or double-strand break repair

• Published in: Nucleic acids research Vol. 46; no. 12; pp. 6238 - 6256
• Main Authors: Bharti, Sanjay Kumar, Sommers, Joshua A, Awate, Sanket, Bellani, Marina A, Khan, Irfan, Bradley, Lynda, King, Graeme A, Seol, Yeonee, Vidhyasagar, Venkatasubramanian, Wu, Yuliang, Abe, Takuye, Kobayashi, Koji, Shin-ya, Kazuo, Kitao, Hiroyuki, Wold, Marc S, Branzei, Dana, Neuman, Keir C, Brosh, Robert M
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 06.07.2018
• Subjects: Nucleic Acid Enzymes
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gky403

Abstract Fanconi Anemia (FA) is characterized by bone marrow failure, congenital abnormalities, and cancer. Of over 20 FA-linked genes, FANCJ uniquely encodes a DNA helicase and mutations are also associated with breast and ovarian cancer. fancj−/− cells are sensitive to DNA interstrand cross-linking (ICL) and replication fork stalling drugs. We delineated the molecular defects of two FA patient-derived FANCJ helicase domain mutations. FANCJ-R707C was compromised in dimerization and helicase processivity, whereas DNA unwinding by FANCJ-H396D was barely detectable. DNA binding and ATP hydrolysis was defective for both FANCJ-R707C and FANCJ-H396D, the latter showing greater reduction. Expression of FANCJ-R707C or FANCJ-H396D in fancj−/− cells failed to rescue cisplatin or mitomycin sensitivity. Live-cell imaging demonstrated a significantly compromised recruitment of FANCJ-R707C to laser-induced DNA damage. However, FANCJ-R707C expressed in fancj-/- cells conferred resistance to the DNA polymerase inhibitor aphidicolin, G-quadruplex ligand telomestatin, or DNA strand-breaker bleomycin, whereas FANCJ-H396D failed. Thus, a minimal threshold of FANCJ catalytic activity is required to overcome replication stress induced by aphidicolin or telomestatin, or to repair bleomycin-induced DNA breakage. These findings have implications for therapeutic strategies relying on DNA cross-link sensitivity or heightened replication stress characteristic of cancer cells.