PROJECT SUMMARY The research described in this program project application employs a broad spectrum of technical approaches and requires highly specialized reagents commonly used among the four participating laboratories. The Molecular Substrates Core (Core B) is designed to ensure the quality of these reagents and to prevent duplicated efforts in setting up specialized preparation procedures. The Core will use streamlined procedures and expertise to produce specialized DNA substrates as needed for each Project within the Program. Aim 1 is to produce site- and lesion-specific crosslinked DNA and DPC substrates. Aim 2 is to generate functional substrates and assay template for in vivo and in vitro studies. Dr. Lei Li will serve as the leader of the Core and will directly supervise all the activities. A Coordinator (Research Laboratory) will manage the day-to-day operations of the Core, in consultation with the Core leader, based on both short-term and long-term needs of each project, and progress will be evaluated in regular team meetings.