Identification and characterization of a novel nuclear structure containing members of the homologous recombination and DNA damage response pathways.

The human RAD9A protein is required for successful execution of the G2/M DNA damage checkpoint. Along with RAD1 and HUS1, RAD9A exists in a heterotrimeric ring-shaped complex which is necessary for activation of the CHK1 checkpoint kinase. RAD9A is also required for proper localization of both TopBP1 and the Claspin adaptor protein during the DNA damage response.

Uncoupling protein-2 is an antioxidant that is up-regulated in the enamel organ of fluoride-treated rats.

Dental fluorosis is characterized by subsurface hypomineralization and retention of enamel matrix proteins. Fluoride (F(-)) exposure generates reactive oxygen species (ROS) that can cause endoplasmic reticulum (ER)-stress. We therefore screened oxidative stress arrays to identify genes regulated by F(-) exposure.

Stress response pathways in ameloblasts: implications for amelogenesis and dental fluorosis.

Human enamel development of the permanent teeth takes place during childhood and stresses encountered during this period can have lasting effects on the appearance and structural integrity of the enamel. One of the most common examples of this is the development of dental fluorosis after childhood exposure to excess fluoride, an elemental agent used to increase enamel hardness and prevent dental caries. Currently the molecular mechanism responsible for dental fluorosis remains unknown; however, recent work suggests dental fluorosis may be the result of activated stress response pathways in ameloblasts during the development of permanent teeth.

Rad9A is required for G2 decatenation checkpoint and to prevent endoreduplication in response to topoisomerase II inhibition.

The Rad9A checkpoint protein interacts with and is required for proper localization of topoisomerase II-binding protein 1 (TopBP1) in response to DNA damage. Topoisomerase II (Topo II), another binding partner of TopBP1, decatenates sister chromatids that become intertwined during replication. Inhibition of Topo II by ICRF-193 (meso-4,4'-(3,2-butanediyl)-bis-(2,6-piperazinedione)), a catalytic inhibitor that does not induce DNA double-strand breaks, causes a mitotic delay known as the G(2) decatenation checkpoint.

The Rad9A checkpoint protein is required for nuclear localization of the claspin adaptor protein.

The interaction between the 911 complex, via Rad9A, and Claspin is required for activation of the Chk1-mediated checkpoint response, along with ATR, TopBp1, and the 911 clamp loader complex Rad17/RFC. Despite the importance of the Rad9A-Claspin interaction in the cell cycle, this interaction has yet to be characterized. In this work we show this interaction persists in a variety of different conditions.