TY - JOUR
T1 - Structural basis for a Polθ helicase small-molecule inhibitor revealed by cryo-EM
AU - Ito, Fumiaki
AU - Li, Ziyuan
AU - Minakhin, Leonid
AU - Chandramouly, Gurushankar
AU - Tyagi, Mrityunjay
AU - Betsch, Robert
AU - Krais, John J.
AU - Taberi, Bernadette
AU - Vekariya, Umeshkumar
AU - Calbert, Marissa
AU - Skorski, Tomasz
AU - Johnson, Neil
AU - Chen, Xiaojiang S.
AU - Pomerantz, Richard T.
N1 - Publisher Copyright:
© The Author(s) 2024.
PY - 2024/7/14
Y1 - 2024/7/14
N2 - DNA polymerase theta (Polθ) is a DNA helicase-polymerase protein that facilitates DNA repair and is synthetic lethal with homology-directed repair (HDR) factors. Thus, Polθ is a promising precision oncology drug-target in HDR-deficient cancers. Here, we characterize the binding and mechanism of action of a Polθ helicase (Polθ-hel) small-molecule inhibitor (AB25583) using cryo-EM. AB25583 exhibits 6 nM IC50 against Polθ-hel, selectively kills BRCA1/2-deficient cells, and acts synergistically with olaparib in cancer cells harboring pathogenic BRCA1/2 mutations. Cryo-EM uncovers predominantly dimeric Polθ-hel:AB25583 complex structures at 3.0-3.2 Å. The structures reveal a binding-pocket deep inside the helicase central-channel, which underscores the high specificity and potency of AB25583. The cryo-EM structures in conjunction with biochemical data indicate that AB25583 inhibits the ATPase activity of Polθ-hel helicase via an allosteric mechanism. These detailed structural data and insights about AB25583 inhibition pave the way for accelerating drug development targeting Polθ-hel in HDR-deficient cancers.
AB - DNA polymerase theta (Polθ) is a DNA helicase-polymerase protein that facilitates DNA repair and is synthetic lethal with homology-directed repair (HDR) factors. Thus, Polθ is a promising precision oncology drug-target in HDR-deficient cancers. Here, we characterize the binding and mechanism of action of a Polθ helicase (Polθ-hel) small-molecule inhibitor (AB25583) using cryo-EM. AB25583 exhibits 6 nM IC50 against Polθ-hel, selectively kills BRCA1/2-deficient cells, and acts synergistically with olaparib in cancer cells harboring pathogenic BRCA1/2 mutations. Cryo-EM uncovers predominantly dimeric Polθ-hel:AB25583 complex structures at 3.0-3.2 Å. The structures reveal a binding-pocket deep inside the helicase central-channel, which underscores the high specificity and potency of AB25583. The cryo-EM structures in conjunction with biochemical data indicate that AB25583 inhibits the ATPase activity of Polθ-hel helicase via an allosteric mechanism. These detailed structural data and insights about AB25583 inhibition pave the way for accelerating drug development targeting Polθ-hel in HDR-deficient cancers.
KW - Cryoelectron Microscopy
KW - Humans
KW - DNA Helicases/metabolism
KW - DNA-Directed DNA Polymerase/metabolism
KW - DNA Polymerase theta
KW - BRCA2 Protein/metabolism
KW - BRCA1 Protein/metabolism
KW - Piperazines/pharmacology
KW - Cell Line, Tumor
KW - Phthalazines/pharmacology
KW - Enzyme Inhibitors/pharmacology
KW - Models, Molecular
KW - Adenosine Triphosphatases/metabolism
KW - Protein Binding
UR - http://www.scopus.com/inward/record.url?scp=85201341729&partnerID=8YFLogxK
U2 - 10.1038/s41467-024-51351-4
DO - 10.1038/s41467-024-51351-4
M3 - Article
C2 - 39143110
AN - SCOPUS:85201341729
SN - 2041-1723
VL - 15
SP - 7003
JO - Nature Communications
JF - Nature Communications
IS - 1
M1 - 7003
ER -
