Single-molecule imaging reveals replication fork coupled formation of G-quadruplex structures hinders local replication stress signaling.

Guanine-rich DNA sequences occur throughout the human genome and can transiently form G-quadruplex (G4) structures that may obstruct DNA replication, leading to genomic instability. Here, we apply multi-color single-molecule localization microscopy (SMLM) coupled with robust data-mining algorithms to quantitatively visualize replication fork (RF)-coupled formation and spatial-association of endogenous G4s. Using this data, we investigate the effects of G4s on replisome dynamics and organization.

Cancer-associated mutations in the iron-sulfur domain of FANCJ affect G-quadruplex metabolism.

FANCJ/BRIP1 is an iron-sulfur (FeS) cluster-binding DNA helicase involved in DNA inter-strand cross-link (ICL) repair and G-quadruplex (G4) metabolism. Mutations in FANCJ are associated with Fanconi anemia and an increased risk for developing breast and ovarian cancer. Several cancer-associated mutations are located in the FeS domain of FANCJ, but how they affect FeS cluster binding and/or FANCJ activity has remained mostly unclear.

The CIA Targeting Complex Is Highly Regulated and Provides Two Distinct Binding Sites for Client Iron-Sulfur Proteins.

The cytoplasmic iron-sulfur assembly (CIA) targeting complex is required for the transfer of an iron-sulfur (Fe-S) cluster to cytoplasmic and nuclear proteins, but how it engages with client proteins is unknown. Here, we show that the complex members MIP18 and CIAO1 associate with the C terminus of MMS19. By doing so, they form a docking site for Fe-S proteins that is disrupted in the absence of either MMS19 or MIP18.