FANCM limits ALT activity by restricting telomeric replication stress induced by deregulated BLM and R-loops

• Published in: Nature communications Vol. 10; no. 1; p. 2253
• Main Authors: Sousa Silva, Bruno Adriano, Pentz, Richard, Figueira, Ana Margarida, Arora, Rajika, Lee, Yong Woo, Hodson, Charlotte, Wischnewski, Harry, Deans, Andrew J., Azzalin, Claus Maria
• Format: Journal Article
• Language: English
• Published: London Springer Nature 28-05-2019; Nature Publishing Group UK; Nature Publishing Group; Nature Portfolio
• Subjects: 13; 13/106; 13/109; 13/31; 13/51; 13/89; 38; 631/67/68; 631/80/103/560; 82/1; 82/80; Adenosine triphosphatase; Cell death; Cell Death - genetics; Cell growth; Cell Line, Tumor; Cell proliferation; Cell Proliferation - genetics; Deactivation; Depletion; Deregulation; DNA biosynthesis; DNA helicase; DNA Helicases - genetics; DNA Helicases - metabolism; DNA Replication - genetics; HEK293 Cells; HeLa Cells; Humanities and Social Sciences; Humans; Inactivation; multidisciplinary; R-loops; RecQ Helicases - genetics; RecQ Helicases - metabolism; Replication; Ribonuclease H - genetics; Ribonuclease H - metabolism; Science; Science (multidisciplinary); Telomerase; Telomere - metabolism; Telomere Homeostasis - genetics; Telomeres; Toxicity; Translocase
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10179-z

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Telomerase negative immortal cancer cells elongate telomeres through the Alternative Lengthening of Telomeres (ALT) pathway. While sustained telomeric replicative stress is required to maintain ALT, it might also lead to cell death when excessive. Here, we show that the ATPase/translocase activity of FANCM keeps telomeric replicative stress in check specifically in ALT cells. When FANCM is depleted in ALT cells, telomeres become dysfunctional, and cells stop proliferating and die. FANCM depletion also increases ALT-associated marks and de novo synthesis of telomeric DNA. Depletion of the BLM helicase reduces the telomeric replication stress and cell proliferation defects induced by FANCM inactivation. Finally, FANCM unwinds telomeric R-loops in vitro and suppresses their accumulation in cells. Overexpression of RNaseH1 completely abolishes the replication stress remaining in cells codepleted for FANCM and BLM. Thus, FANCM allows controlled ALT activity and ALT cell proliferation by limiting the toxicity of uncontrolled BLM and telomeric R-loops.
Research in the Azzalin laboratory was supported by the Swiss National Science Foundation (31003A_160338), the European Molecular Biology Organization (IG3576) and the Fundação para a Ciência e a Tecnologia (IF/01269/2015; PTDC/MED-ONC/28282/2017; PTDC/BIA-MOL/29352/2017). R.P. was supported by a Swiss National Science Foundation Doc.Mobility fellowship (P1EZP3-168771). Research in the Deans laboratory was supported by the Cancer Council of Victoria, Australian National Health and Medical Research Council (APP1139099), Buxton trust and the Victorian Government’s OIS Program. A.J.D is a Victorian Cancer Agency fellow. Publication costs were supported by UID/BIM/50005/2019, project funded by the Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through Fundos do Orçamento de Estado.