DNA polymerase eta (Polη η η η ) is responsible for efficient translesion synthesis (TLS) past cis-syn cyclobutane thymine dimers (TT dimers), the major DNA lesions induced by UV irradiation. Loss of human Polη η η η leads to xeroderma pigmentosum variant syndrome, clearly indicating that Polη η η η plays a vital role in preventing skin cancer caused by exposure to sunlight. To further examine Polη η η η functions and the mechanisms that regulate this important protein, Polη η η η complexes were purified from HeLa cells over-expressing epitope-tagged Polη η η η , and polypeptides associated with Polη η η η , including Rad18, Rad6 and Rev1, were identified by a combination of mass spectrometry and Western blot analysis. The chromatin-bound fractions of cells subjected to UV irradiation, S phase synchronization, or S phase arrest were specifically enriched in such complexes. These results suggest that arrested replication forks strengthen interactions among Polη η η η , Rad18/Rad6 and Rev1, consistent with the requirement for effective TLS by Polη η η η at sites of DNA lesions.

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Low cycle fatigue life of structural materials diminishes remarkably as functions of various parameters in high temperature water simulating LWR coolant. Such reduction was estimated by the fatigue life reduction factor (Fen) and the equations to calculate Fen were developed and have undergone revision over the past ten years. The authors have endeavored to establish the method assessing fatigue damage at LWR power plants for the past 13 years in the Japanese EFT (Environmental Fatigue Tests) project under the financial support from the JNES (Japan Nuclear Safety Organization). The project terminated at the end of March in 2007. Final proposals of Fen equations were established for carbon, low-alloy, and austenitic stainless steels and nickel base alloys based on all the data obtained in the project. As the results, a small change in saturated strain rate for carbon and low-alloy steels in highly dissolved oxygen water and newly revised equations including slight change in saturated strain rate for stainless steels in BWR water as well as those for nickel base alloys were proposed. The difference between revised and previous model is essentially not large.