Multiple Defects Sensitize p53-Deficient Head and Neck Cancer Cells to the WEE1 Kinase Inhibition.

The p53 gene is the most commonly mutated gene in solid tumors, but leveraging p53 status in therapy remains a challenge. Previously, we determined that p53 deficiency sensitizes head and neck cancer cells to AZD1775, a WEE1 kinase inhibitor, and translated our findings into a phase I clinical trial. Here, we investigate how p53 affects cellular responses to AZD1775 at the molecular level.

Class I Histone Deacetylase HDAC1 and WRN RECQ Helicase Contribute Additively to Protect Replication Forks upon Hydroxyurea-induced Arrest.

The WRN helicase/exonuclease is mutated in Werner syndrome of genomic instability and premature aging. WRN-depleted fibroblasts, although remaining largely viable, have a reduced capacity to maintain replication forks active during a transient hydroxyurea-induced arrest. A strand exchange protein, RAD51, is also required for replication fork maintenance, and here we show that recruitment of RAD51 to stalled forks is reduced in the absence of WRN.

Application of the microfluidic-assisted replication track analysis to measure DNA repair in human and mouse cells.

Functional studies of the roles that DNA helicases play in human cells have benefited immensely from DNA fiber (or single molecule) technologies, which enable us to discern minute differences in behaviors of individual replication forks in genomic DNA in vivo. DNA fiber technologies are a group of methods that use different approaches to unravel and stretch genomic DNA to its contour length, and display it on a glass surface in order to immuno-stain nucleoside analog incorporation into DNA to reveal tracks (or tracts) of replication. We have previously adopted a microfluidic approach to DNA stretching and used it to analyze DNA replication.

Mitomycin C reduces abundance of replication forks but not rates of fork progression in primary and transformed human cells.

DNA crosslinks can block replication and slow down S phase progression . We characterized the effect of mitomycin C crosslinker on S phase globally and on individual replication forks in wild type and FANCD2-deficient human cells. FANCD2 is critical to crosslink repair, and is also implicated in facilitating DNA replication.

Distinct functions of human RECQ helicases WRN and BLM in replication fork recovery and progression after hydroxyurea-induced stalling.

Human WRN and BLM genes are members of the conserved RECQ helicase family. Mutations in these genes are associated with Werner and Bloom syndromes. WRN and BLM proteins are implicated in DNA replication, recombination, repair, telomere maintenance, and transcription.

Tumor growth is suppressed in mice expressing a truncated XRCC1 protein.

Tumor progression depends on the support of cells in the microenvironment, and is driven in part by the generation of reactive oxygen species (ROS). ROS can damage DNA, and the repair of damaged DNA is a well-known process involved in tumor initiation and promotion, but the role of DNA repair in tumor progression is not fully understood. In this regard the X-ray cross complementing 1 (XRCC1) protein is known to orchestrate the assembly of repair complexes at sites of DNA single strand breaks either directly or indirectly through repair of damaged bases, largely as the result of ROS-induced damage.