A small molecule inhibitor of the BLM helicase modulates chromosome stability in human cells.

The Bloom's syndrome protein, BLM, is a member of the conserved RecQ helicase family. Although cell lines lacking BLM exist, these exhibit progressive genomic instability that makes distinguishing primary from secondary effects of BLM loss problematic. In order to be able to acutely disable BLM function in cells, we undertook a high throughput screen of a chemical compound library for small molecule inhibitors of BLM.

Interaction between the helicases genetically linked to Fanconi anemia group J and Bloom's syndrome.

Bloom's syndrome (BS) and Fanconi anemia (FA) are autosomal recessive disorders characterized by cancer and chromosomal instability. BS and FA group J arise from mutations in the BLM and FANCJ genes, respectively, which encode DNA helicases. In this work, FANCJ and BLM were found to interact physically and functionally in human cells and co-localize to nuclear foci in response to replication stress.

Ku70 corrupts DNA repair in the absence of the Fanconi anemia pathway.

A conserved DNA repair response is defective in the human genetic illness Fanconi anemia (FA). Mutation of some FA genes impairs homologous recombination and error-prone DNA repair, rendering FA cells sensitive to DNA cross-linking agents. We found a genetic interaction between the FA gene FANCC and the nonhomologous end joining (NHEJ) factor Ku70.

FANCJ is a structure-specific DNA helicase associated with the maintenance of genomic G/C tracts.

Fanconi anemia (FA) is a heritable human cancer-susceptibility disorder, delineating a genetically heterogenous pathway for the repair of replication-blocking lesions such as interstrand DNA cross-links. Here we demonstrate that one component of this pathway, FANCJ, is a structure-specific DNA helicase that dissociates guanine quadruplex DNA (G4 DNA) in vitro. Moreover, in contrast with previously identified G4 DNA helicases, such as the Bloom's helicase (BLM), FANCJ unwinds G4 substrates with 5'-3' polarity.

The Human RecQ helicases, BLM and RECQ1, display distinct DNA substrate specificities.

RecQ helicases maintain chromosome stability by resolving a number of highly specific DNA structures that would otherwise impede the correct transmission of genetic information. Previous studies have shown that two human RecQ helicases, BLM and WRN, have very similar substrate specificities and preferentially unwind noncanonical DNA structures, such as synthetic Holliday junctions and G-quadruplex DNA. Here, we extend this analysis of BLM to include new substrates and have compared the substrate specificity of BLM with that of another human RecQ helicase, RECQ1.

UBE2T, the Fanconi anemia core complex, and FANCD2 are recruited independently to chromatin: a basis for the regulation of FANCD2 monoubiquitination.

The Fanconi anemia (FA) nuclear core complex and the E2 ubiquitin-conjugating enzyme UBE2T are required for the S phase and DNA damage-restricted monoubiquitination of FANCD2. This constitutes a key step in the FA tumor suppressor pathway, and much attention has been focused on the regulation at this point. Here, we address the importance of the assembly of the FA core complex and the subcellular localization of UBE2T in the regulation of FANCD2 monoubiquitination.

The vertebrate Hef ortholog is a component of the Fanconi anemia tumor-suppressor pathway.

The helicase-associated endonuclease for fork-structured DNA (Hef) is an archaeabacterial protein that processes blocked replication forks. Here we have isolated the vertebrate Hef ortholog and investigated its molecular function. Disruption of this gene in chicken DT40 cells results in genomic instability and sensitivity to DNA cross-links.

The Fanconi anaemia gene FANCC promotes homologous recombination and error-prone DNA repair.

The Fanconi anemia (FA) protein FANCC is essential for chromosome stability in vertebrate cells, a feature underscored by the extreme sensitivity of FANCC-deficient cells to agents that crosslink DNA. However, it is not known how this FA protein facilitates the repair of both endogenously acquired and mutagen-induced DNA damage. Here, we use the model vertebrate cell line DT40 to address this question.

FANCE: the link between Fanconi anaemia complex assembly and activity.

The Fanconi anaemia (FA) nuclear complex (composed of the FA proteins A, C, G and F) is essential for protection against chromosome breakage. It activates the downstream protein FANCD2 by monoubiquitylation; this then forges an association with the BRCA1 protein at sites of DNA damage. Here we show that the recently identified FANCE protein is part of this nuclear complex, binding both FANCC and FANCD2.