Understanding Structural And Functional Mechanisms of Emi1 Inhibition of the Anaphase Promoting Complex

Healthy, reproducing cells create and destroy proteins in an ordered manner. Both the concentration and localization of protein pools is important to regulate the many cellular processes necessary for the life of the cell. In order to produce new proteins, cells degrade existing materials such as proteins and organelles that are dispensable or troublesome in order to recycle their raw components. Degradation is accomplished largely through two major pathways: in bulk through processes such as autophagy and phagocytosis, or in a targeted manner through the ubiquitin-proteasome pathway. Autophagy utilizes an encompassing body to encapsulate targets and surrounding materials for decomposition in a regulated but relatively non-specific manner. The ubiquitin-proteasome pathway, however, is an exquisitely precise method of degradation capable of targeting specific pools of protein substrates. So-called ubiquitination generates a signal for degradation by the 26S proteasome machinery. In order to establish the degradation signal, the cell utilizes a cascade of 3 enzymes working in concert to organize substrates and ubiquitin. By using enzymes capable of substrate specificity, the cell can regulate large pools of proteins in a specific spatio-temporal manner. In the present study, we employ biochemical and structure-based techniques to study proteins involved in an essential ubiquitination pathway involved in maintenance of the cell cycle. A mitotic regulator called the Anaphase Promoting Complex, also called Cyclosome (APC/C), modifies myriad substrates that control cell cycle activities. The APC/C is a ubiquitin ligase complex; it is the final enzyme in a tri-enzyme cascade and catalyzes the final step of Ub transfer from an E2 enzyme directly to substrates. A protein called Emi1 is responsible for directly binding and inhibiting the APC/C throughout interphase, when APC/C substrates are stabilized. We set out to study domains of Emi1 responsible for binding and inhibiting the APC/C and its association with E2 enzymes or substrates, with the aim of charcterizing both the mechanism of the inhibitor and the essential functional requirements of the APC/C, which are not well understood. We aim to visualize the APC/C in complex with Emi1 through electron microscopy and to accurately interpret the location and orientation of Emi1 within this density. The APC/C is a large, ~1,200 kDa multi-protein complex, and Emi1 is a single protein of only 50 kDa. Despite its small size, even a small subdomain of Emi1 potently inhibits the APC/C through a combination of not well-characterized mechanisms. Emi1 has an APC/C recognition motif called a D-box that is typically found within APC/C substrates. Emi1’s D-box is recruited to the substrate-binding sites of APC/C and serves as a pseudo-substrate inhibitor. Emi1 also inhibits through distinct mechanisms both of the E2 enzymes that coordinate with APC/C function. An essential, folded Zinc-binding Region (ZBR) and a helical “Linker” sequence cooperate to bind and block APC/C from recruiting one of two APC-specific E2 enzymes, Ubch10. Emi1 also has a conserved C-terminal motif, with charge and sequence similar to the other APC/C- specific E2 enzyme, Ube2s. Emi1 competes directly with Ube2s for APC/C recruitment, and it is through the combination of these three mechanisms that are afforded by many motifs within Emi1, that makes Emi1 a potent APC/C inhibitor. When associated with Emi1, the APC/C is inefficient at both recruiting substrates and binding E2 enzymes, allowing for stabilization of APC/C substrates, which is important for regulation of timing of cell cycle processes

Should New Zealand Adopt Say on Pay?

article published in law journalAround the globe, the latest fashion in corporate governance circles is "Say on Pay," a shareholder vote – sometimes precatory, other times mandatory – on CEO remuneration. Country after country has adopted Say on Pay in response to shareholder disgust over the size of CEO pay packets. Beginning with the U.K., and later followed by the Netherlands, Australia, Sweden, Norway, Belgium, France, Switzerland, and the U.S., there has been a widespread acceptance of the shareholder vote on executive pay around the world. In this article, we ask the question: Should New Zealand follow the crowd and adopt Say on Pay, or should it continue down its own path, leaving directors with near total control over executive remuneration levels? Academics are divided over the desirability of Say on Pay – those that believe in strong managerial power are firmly against it, while shareholder activists come out heavily in its favor. The main theoretical arguments revolve around whether: it will tip the balance of power against managers; shareholders are competent to evaluate executive remuneration; third party voting advisors will gain too much power if it is enacted; there will be any reduction in the size, and rate of growth, of CEO pay packets; and it will strengthen the relationship between pay and performance. The experience in the U.K. and the U.S. to date sheds some light on the validity of these arguments. On average, shareholders have voted strongly in favor of executive pay practices at most companies. Say on Pay seems to have had little impact on the size and growth of average CEO pay, but it does appear to have impacted pay practices at poorly performing companies that have unusually high pay. There is a greater level of engagement between shareholders and managers on pay issues at many companies, and firms have become more responsive to negative shareholder Say on Pay votes. Third party voting advisors, such as Institutional Shareholder Services, have become important corporate governance players, whose recommendations have a significant impact on shareholder voting outcomes. In light of these academic arguments, and practical experience in the U.K. and U.S., we believe that New Zealand should carefully consider whether to adopt Say on Pay. We do not view the evidence as compelling the conclusion that Say on Pay is essential, but we can understand why some shareholders might want to see it implemented. However, the existing evidence shows that it is unlikely to have a big effect on current pay practices at most companies in New Zealand if it is adopted

Kaluza-Klein Excitations of W and Z at the LHC?

Deviations from standard electroweak physics arise in the framework of a Randall-Sundrum model, with matter and gauge fields in the bulk and the Higgs field localized on the TeV brane. We focus in particular on modifications associated with the weak mixing angle. Comparison with the electroweak precision data yields a rather stringent lower bound of about 10 TeV on the masses of the lowest Kaluza-Klein excitation of the W and Z bosons. With some optimistic assumptions the bound could be lowered to about 7 TeV.Comment: 11 pages, 5 figures, comments and references adde

Some Phenomenological Aspects of the (n + m + 1) dimensional Brane World Scenario with an m-form Field

In the D = (n + m + 1) dimensional brane world scenario with m compact dimensions, the radion modulus can be stabilised by a massive bulk m-form antisymmetric field. We analyse some of the phenomenological aspects of this scenario. We find that the radion mass is smaller than the TeV scale, but larger than that in the case where the radion modulus is stabilised by a bulk scalar field. From the macroscopic n dimensional spacetime point of view, the m-form field mimics a set of p-form fields. We analyse the mass spectrum of these fields. The lowest mass is \stackrel{>}{_\sim} TeV whereas, for any bulk or brane field, the excitations in the compact space have Planckian mass and are likely to reintroduce the hierarchy problem. Also, we analyse the couplings of the m-form field to the matter fields living on a brane. The present results are applicable to more general cases also.Comment: 15 pages. Latex. References added. Many minor changes. Correct analysis of Kaluza-Klein excitations along compact brane directions shows that the hierarchy problem is very likely reintroduced. To appear in Physics Letters

Appreciative Methods Applied to the Assessment of Complex Systems

Complex systems have characteristics that challenge traditional systems engineering processes and methods. These characteristics have been defined in various ways. INCOSE has previously identified characteristics of complex systems and potential methods to deal with complexity in system development. The purpose of this paper is to provide definitions and describe distinguishing characteristics of complexity using example systems to illustrate approaches to assessing the extent of complexity. The paper applies Appreciative Inquiry to identify and assess complex system characteristics. The characteristics are used to examine several different examples of systems to illuminate areas of complexity. These examples range from seemingly simple systems to complicated systems to complex systems. Different tiers of complexity are identified as a result of the assessment. The paper also identified and introduces topics on managing complexity and the integrating system perspective that represent new directions for the engineering of complex systems. The Appreciative Inquiry approach provides a method for systems engineering practitioners to more readily identify complexity when they encounter it, and to deal more effectively with this complexity once it has been identified

Appreciative Methods Applied to the Assessment of Complex Systems

No abstract availabl

Homelessness and the meaning of home: rooflessness or rootlessness?

This paper has several objectives. These are: (1) to analyse the meaning of homelessness in the light of recent contributions on the meaning of home: (2) to criticize some current perspectives on homelessness as a social problem; (3) to identify and explore a number of different dimensions of the meaning of home and homelessness; (4) to reassess the evidence on the context of home and homelessness, and re-examine the meaning of homelessness in the light of that reassessed evidence; and (5) to explain the political meaning of homelessness as expressed in official definitions, legislation and state provision (or lack of it)

Risk of colon cancer in hereditary non-polyposis colorectal cancer patients as predicted by fuzzy modeling: Influence of smoking

AIM: To investigate whether a fuzzy logic model could predict colorectal cancer (CRC) risk engendered by smoking in hereditary non-polyposis colorectal cancer (HNPCC) patients. METHODS: Three hundred and forty HNPCC mismatch repair (MMR) mutation carriers from the Creighton University Hereditary Cancer Institute Registry were selected for modeling. Age-dependent curves were generated to elucidate the joint effects between gene mutation (hMLH1 or hMSH2), gender, and smoking status on the probability of developing CRC. RESULTS: Smoking significantly increased CRC risk in male hMSH2 mutation carriers (P \u3c 0.05). hMLH1 mutations augmented CRC risk relative to hMSH2 mutation carriers for males (P \u3c 0.05). Males had a significantly higher risk of CRC than females for hMLH1 non smokers (P \u3c 0.05), hMLH1 smokers (P \u3c 0.1) and hMSH2 smokers (P \u3c 0.1). Smoking promoted CRC in a dose-dependent manner in hMSH2 in males (P \u3c 0.05). Females with hMSH2 mutations and both sexes with the hMLH1 groups only demonstrated a smoking effect after an extensive smoking history (P \u3c 0.05). CONCLUSION: CRC promotion by smoking in HNPCC patients is dependent on gene mutation, gender and age. These data demonstrate that fuzzy modeling may enable formulation of clinical risk scores, thereby allowing individualization of CRC prevention strategies