It is also possible that different ethnicities account for the observed differencesbetween cohorts. Based on the Boston cohort, our study protocol was modified by the inclusion of severe pancreatitis as a predisposing condition for ARDS. Severe pancreatitis is a well-established risk factor for the development of ARDS and is frequently observed in critically ill patients in China. In the Beijing cohort, we identified 23 cases of severe pancreatitis, similar to a Bortezomib abmole bioscience previous report of 15.6% in a large Chinese ICU ONX-0914 abmole bioscience survey. About 52% of severe pancreatitis cases eventually developed ARDS during ICU admission. Severe pancreatitis was not associated with ARDS risk, but was associated with lower mortality. However, the Beijing study is limited by a small sample size. With the patients’ enrollment keeps, we will further evaluate severe pancreatitis as a clinically important factor in the development and outcome of ARDS. To maintain homeostasis or to undergo specified developmental decisions, an organism must be able to respond rapidly to a variety of environmental changes. Protein turnover plays a critical role in the control of many signaling pathways. More than 80% of all proteins are estimated to be degraded via the ubiqutin-proteasome system. Protein ubiquitination is an enzymatic cascade in which ubiquitin is activated by an E1 enzyme, transferred to an E2 ubiquitin-conjugating enzyme and then transferred to a substrate selected by an E3 ubiquitin ligase. An E3 ubiquitin ligase must rapidly and uniquely bind to target proteins in response to stimuli. One of the best characterized E3s are the S phase kinase-associated protein 1 –cullin 1 –F-box protein type ubiquitin ligase complexes. CUL1 serves as a scaffold for assembling the ubiquitin-conjugating machinery. The C-terminus of CUL1 interacts with the RING-box protein 1, whereas its N- terminus binds to SKP1, which, in turn, binds to an F-box protein. F-box proteins contain an N-terminal 48-amino-acid F-box domain, which binds to SKP1 to create a link to CUL1. In addition, F-box proteins generally contain Cterminal variable protein-interaction domains, such as Trp–Asp repeats and leucine-rich repeats, as well as unknown motifs, which are responsible for binding specific substrates. As a core component of UPS, F-box proteins are involved in a wide range of cellular processes, from cell cycle control to gene transcription and organism development. Given this critical role, misregulation of F-box protein-mediated ubiquitination has been implicated in many human diseases, such as cancers and viral infections. The number of F-box genes varies dramatically even among closely related species. For instance, lineage-specific expansion has been found in annual Arabidopsis but not in the perennial Populus, suggesting an adaptive advantage conferred by F-box genes for particular physiological processes in Arabidopsis. Given the wide involvement of F-box proteins in cellular processes in human cells, pursuing research on the evolution of F-box proteins in humans and other closely related species is very important. However, most previous works in the field have focused on the evolutionary pattern of F-box genes only in plants, where F-box gene expansion was more frequent.