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Biochemical properties of naturally occurring human bloom helicase variants

Bloom syndrome helicase (BLM) is a RecQ-family helicase implicated in a variety of cellular processes, including DNA replication, DNA repair, and telomere maintenance. Mutations in human BLM cause Bloom syndrome (BS), an autosomal recessive disorder that leads to myriad negative health impacts inclu...

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Autores principales: Cueny, Rachel R., Varma, Sameer, Schmidt, Kristina H., Keck, James L.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10237670/
https://www.ncbi.nlm.nih.gov/pubmed/37267408
http://dx.doi.org/10.1371/journal.pone.0281524
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author Cueny, Rachel R.
Varma, Sameer
Schmidt, Kristina H.
Keck, James L.
author_facet Cueny, Rachel R.
Varma, Sameer
Schmidt, Kristina H.
Keck, James L.
author_sort Cueny, Rachel R.
collection PubMed
description Bloom syndrome helicase (BLM) is a RecQ-family helicase implicated in a variety of cellular processes, including DNA replication, DNA repair, and telomere maintenance. Mutations in human BLM cause Bloom syndrome (BS), an autosomal recessive disorder that leads to myriad negative health impacts including a predisposition to cancer. BS-causing mutations in BLM often negatively impact BLM ATPase and helicase activity. While BLM mutations that cause BS have been well characterized both in vitro and in vivo, there are other less studied BLM mutations that exist in the human population that do not lead to BS. Two of these non-BS mutations, encoding BLM P868L and BLM G1120R, when homozygous, increase sister chromatid exchanges in human cells. To characterize these naturally occurring BLM mutant proteins in vitro, we purified the BLM catalytic core (BLM(core), residues 636–1298) with either the P868L or G1120R substitution. We also purified a BLM(core) K869A K870A mutant protein, which alters a lysine-rich loop proximal to the P868 residue. We found that BLM(core) P868L and G1120R proteins were both able to hydrolyze ATP, bind diverse DNA substrates, and unwind G-quadruplex and duplex DNA structures. Molecular dynamics simulations suggest that the P868L substitution weakens the DNA interaction with the winged-helix domain of BLM and alters the orientation of one lobe of the ATPase domain. Because BLM(core) P868L and G1120R retain helicase function in vitro, it is likely that the increased genome instability is caused by specific impacts of the mutant proteins in vivo. Interestingly, we found that BLM(core) K869A K870A has diminished ATPase activity, weakened binding to duplex DNA structures, and less robust helicase activity compared to wild-type BLM(core). Thus, the lysine-rich loop may have an important role in ATPase activity and specific binding and DNA unwinding functions in BLM.
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spelling pubmed-102376702023-06-03 Biochemical properties of naturally occurring human bloom helicase variants Cueny, Rachel R. Varma, Sameer Schmidt, Kristina H. Keck, James L. PLoS One Research Article Bloom syndrome helicase (BLM) is a RecQ-family helicase implicated in a variety of cellular processes, including DNA replication, DNA repair, and telomere maintenance. Mutations in human BLM cause Bloom syndrome (BS), an autosomal recessive disorder that leads to myriad negative health impacts including a predisposition to cancer. BS-causing mutations in BLM often negatively impact BLM ATPase and helicase activity. While BLM mutations that cause BS have been well characterized both in vitro and in vivo, there are other less studied BLM mutations that exist in the human population that do not lead to BS. Two of these non-BS mutations, encoding BLM P868L and BLM G1120R, when homozygous, increase sister chromatid exchanges in human cells. To characterize these naturally occurring BLM mutant proteins in vitro, we purified the BLM catalytic core (BLM(core), residues 636–1298) with either the P868L or G1120R substitution. We also purified a BLM(core) K869A K870A mutant protein, which alters a lysine-rich loop proximal to the P868 residue. We found that BLM(core) P868L and G1120R proteins were both able to hydrolyze ATP, bind diverse DNA substrates, and unwind G-quadruplex and duplex DNA structures. Molecular dynamics simulations suggest that the P868L substitution weakens the DNA interaction with the winged-helix domain of BLM and alters the orientation of one lobe of the ATPase domain. Because BLM(core) P868L and G1120R retain helicase function in vitro, it is likely that the increased genome instability is caused by specific impacts of the mutant proteins in vivo. Interestingly, we found that BLM(core) K869A K870A has diminished ATPase activity, weakened binding to duplex DNA structures, and less robust helicase activity compared to wild-type BLM(core). Thus, the lysine-rich loop may have an important role in ATPase activity and specific binding and DNA unwinding functions in BLM. Public Library of Science 2023-06-02 /pmc/articles/PMC10237670/ /pubmed/37267408 http://dx.doi.org/10.1371/journal.pone.0281524 Text en © 2023 Cueny et al https://creativecommons.org/licenses/by/4.0/This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Cueny, Rachel R.
Varma, Sameer
Schmidt, Kristina H.
Keck, James L.
Biochemical properties of naturally occurring human bloom helicase variants
title Biochemical properties of naturally occurring human bloom helicase variants
title_full Biochemical properties of naturally occurring human bloom helicase variants
title_fullStr Biochemical properties of naturally occurring human bloom helicase variants
title_full_unstemmed Biochemical properties of naturally occurring human bloom helicase variants
title_short Biochemical properties of naturally occurring human bloom helicase variants
title_sort biochemical properties of naturally occurring human bloom helicase variants
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10237670/
https://www.ncbi.nlm.nih.gov/pubmed/37267408
http://dx.doi.org/10.1371/journal.pone.0281524
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