RECON syndrome is a genome instability disorder caused by mutations in the DNA helicase RECQL1
Bassam Abu-Libdeh, … , Robert M. Brosh Jr., Grant S. Stewart
Bassam Abu-Libdeh, … , Robert M. Brosh Jr., Grant S. Stewart
Published January 13, 2022
Citation Information: J Clin Invest. 2022;132(5):e147301. https://doi.org/10.1172/JCI147301.
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Research Article Cell biology Genetics

RECON syndrome is a genome instability disorder caused by mutations in the DNA helicase RECQL1

Abstract

Despite being the first homolog of the bacterial RecQ helicase to be identified in humans, the function of RECQL1 remains poorly characterized. Furthermore, unlike other members of the human RECQ family of helicases, mutations in RECQL1 have not been associated with a genetic disease. Here, we identify 2 families with a genome instability disorder that we have named RECON (RECql ONe) syndrome, caused by biallelic mutations in the RECQL gene. The affected individuals had short stature, progeroid facial features, a hypoplastic nose, xeroderma, and skin photosensitivity and were homozygous for the same missense mutation in RECQL1 (p.Ala459Ser), located within its zinc binding domain. Biochemical analysis of the mutant RECQL1 protein revealed that the p.A459S missense mutation compromised its ATPase, helicase, and fork restoration activity, while its capacity to promote single-strand DNA annealing was largely unaffected. At the cellular level, this mutation in RECQL1 gave rise to a defect in the ability to repair DNA damage induced by exposure to topoisomerase poisons and a failure of DNA replication to progress efficiently in the presence of abortive topoisomerase lesions. Taken together, RECQL1 is the fourth member of the RecQ family of helicases to be associated with a human genome instability disorder.

Authors

Bassam Abu-Libdeh, Satpal S. Jhujh, Srijita Dhar, Joshua A. Sommers, Arindam Datta, Gabriel M.C. Longo, Laura J. Grange, John J. Reynolds, Sophie L. Cooke, Gavin S. McNee, Robert Hollingworth, Beth L. Woodward, Anil N. Ganesh, Stephen J. Smerdon, Claudia M. Nicolae, Karina Durlacher-Betzer, Vered Molho-Pessach, Abdulsalam Abu-Libdeh, Vardiella Meiner, George-Lucian Moldovan, Vassilis Roukos, Tamar Harel, Robert M. Brosh Jr., Grant S. Stewart

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Figure 3

The p.A459S mutation compromises the ability of RECQL1 to remodel reversed replication forks but not its ability to catalyze SSA.

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The p.A459S mutation compromises the ability of RECQL1 to remodel revers...
(A) Depiction of the reversed and replication fork substrates used in this experiment. The black dot and “X” in the figure represent an isocytosine base and mismatched bases, respectively. These were added to minimize spontaneous conversion of the reversed fork into a replication fork. The asterisk indicates the 5′ end of the oligonucleotide that was radiolabeled with 32P. (B) WT or A459S RECQL1 (20 nM) was incubated with 2 nM radiolabeled reversed fork substrate at 37°C for the indicated durations. A radiolabeled replication fork (2 nM, black triangle) was included as a marker. A representative gel is shown. (C) Quantitation of DNA unwinding from 3 independent experiments, with the SEM shown. AUC: WT (mean ± SEM: 709.5 ± 35.23); A459S (mean ± SEM: 174.4 ± 23.91). WT versus A459S AUC: P < 0.0002, by unpaired t test. (D and E) RECQL1 strand annealing activity was assessed by the formation of a 19 bp forked duplex DNA molecule from 2 partially complementary single-stranded oligonucleotides as a function of increasing RECQL1 concentration. (D) Two partially complementary oligonucleotides (1 radiolabeled at the 5′ end and the other unlabeled; 0.5 nM of each was incubated with the indicated concentrations of RECQL1 for 15 minutes at 37°C in the absence of ATP). A 19 bp forked duplex was loaded as a marker. Representative gel images are shown. (E) Quantitation of strand annealing activity from 3 independent experiments, with the SEM shown.