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Artemis, a member of the SNM1 gene family, is a known phosphorylation target of ATM, ATR, and DNA-PKcs. We have previously identified two serine residues in Artemis (Ser[sup516] and Ser[sup645]) that are subject to phosphorylation by ATM and are involved in mediating recovery from the G[sub2]/M checkpoint in response to ionizing radiation. Here we show that these same sites are also phosphorylated by ATR in response to various types of replication stress including UVC, aphidicolin, and hydroxyurea. We also show that mutation of the Ser[sup516] and Ser[sup645] residues causes a prolonged S phase checkpoint recovery after treatment with UV or aphidicolin, and that this delayed recovery process coincides with a prolonged stabilization of cyclin E and down-regulation of Cdk2 kinase activity. Furthermore, we show that Artemis interacts with the F-box protein Fbw7, and that this interaction regulates cyclin E degradation through the SCF[supFbW7] E3 ubiquitin ligase complex. The interaction between Artemis and Fbw7 is regulated by phosphorylation of Ser[sup516] and Ser[sup645] sites that occur in response to replication stress. Thus, our findings suggest a novel pathway of recovery from the S phase checkpoint in that in response to replication stress phosphorylation of Artemis by ATR enhances its interaction with Fbw7, which in turn promotes ubiquitylation and the ultimate degradation of cyclin E. [ABSTRACT FROM AUTHOR]

We report on the speciation of sulfate, nitrate with special attention to their ammonium salts during 1999–2000 in Beijing. Higher concentrations in fine particles were observed for ammonium sulfate and other sulfates during winter. Ammonium sulfate concentration ranged from 2.78 to 23.7 μg m−3 in fine particles, and ranged from 0.15 to 1.39 μg m−3 in coarse particles. Other sulfate concentrations ranged from 1.51 to 11.9 μg m−3 in fine particles, and ranged from 0.10 to 1.00 μg m−3 in coarse particles. Ammonium nitrate was mainly in fine particles with the highest concentration in December (11.9 μg m−3). Other nitrates were mainly distributed in the particles of 2.1–4.7 μm with concentrations ranged between 0.36 and 2.54 μg m−3, and the highest concentration of other nitrates was observed in fine particles in January (9.32 μg m−3). XRD analysis showed that ammonium sulfates existed in different forms in atmospheric aerosols. The results suggested the importance of heterogeneous formations of sulfate and nitrate in Beijing especially in winter. [Copyright &y& Elsevier]