MARC WALLACE KIRSCHNER

..By applying control analysis to our mathematical model, we demonstrate the modular design, sensitivity, and robustness of the Wnt pathway and derive an explicit expression for tumor suppression and oncogenicity...

..Evolvability may have been generally selected in the course of selection for robust, flexible processes suitable for complex development and physiology and specifically selected in lineages undergoing repeated radiations...

..In this review, I attempt to trace the curious history of intracellular protein degradation, its novel and elegant biochemistry and to extract the features that might be important for the next era of studies in cell physiology...

..Thus, Mat89Bb plays an evolutionarily conserved role as a crucial regulator of both cell cycle and development...

..These approaches were validated and subsequently applied to the phosphorylation of the yeast transcription factor Pho4...

..We speculate that the protein, which we have named sororin, regulates the ability of the cohesin complex to mediate sister chromatid cohesion, perhaps by altering the nature of the interaction of cohesin with the chromosomes...

....

..All these considerations have motivated a search for other techniques to assist in identifying substrates of this particular E3 ligase. Here, we describe the use of in vitro expression cloning to identify novel APC substrates...

..The processivity of multiubiquitination is strongly influenced by the D box within the substrate, suggesting that substrate ordering is established by a mechanism intrinsic to APC and its substrates and similar to kinetic proofreading...

..Inhibition of ERK activation partially inhibits T48 phosphorylation, Cdc25C activation, and mitotic induction. These findings demonstrate that ERK-MAP kinases are directly involved in activating Cdc25 during the G(2)/M transition...

....

..This indicates that the core of the metazoan cell cycle could be described as a self-perpetuating but highly regulated oscillator composed of alternating CDK and APC activities...

..The complex is organized around a core of Nap and Abi. Sra is a peripheral subunit recruited on the Nap side, whereas the Wave and Hspc subunits are recruited on the Abi side of the core...

..We discuss these findings in terms of the variable efficacy of antimitotic drugs in cancer chemotherapy...

..The newly discovered p53-induced p53R2 protein that lacks a KEN box may supply deoxyribonucleotides for DNA repair during G(0)G(1)...

..Degradation of Tome-1 during G1 allows for wee 1 accumulation during interphase, thereby providing a critical link between the APC and SCF pathways in regulation of cdk1/cyclin B activity and thus mitotic entry and exit...

..The methods described here represent focused, alternative approaches for studying the dynamically changing proteome...

..The cleaved fragments remain associated with each other and are catalytically active. Mapping of the cleavage sites reveals that all three sites are conserved in vertebrates underlining a significant function for this regulation...

..Consistent with this finding, clustering of Nck by a 12-residue Tir phosphopeptide triggered actin tail formation in Xenopus egg extracts...

..As a result, accumulation of SCF(SKP2) requires prior inactivation of APC(CDH1). These findings provide an insight into the orchestration of SCF and APC activities during cell-cycle progression, and into the involvement of the APC in G1...

....

..Thus, CD437 modulates the expression of E2F-1 and cyclin B through the simultaneous stimulation and inhibition of the cyclin B and E2F-1 E3 ligases, respectively...

..The data suggest that the distinction between the two Wnt classes lies not in intrinsic differences in the molecules but via the Frizzled molecules with which they interact...

..Finally, brains of mcph1 adult male flies have defects in mushroom body structure, suggesting an evolutionarily conserved role for MCPH1 in brain development...

..This orthogonality suggests continued selection for physiological adaptability and hints at a role for this adaptability in evolutionary change...

..This work introduces a general method for using low-micromolar chemical inhibitors to identify both inhibitor targets and other components of a signaling pathway...

..In this chapter, we describe the preparation of the components used in these purified actin assembly reactions, as well as the assay conditions under which we monitor actin polymerization kinetics in vitro...

..Finally we provide a protocol for immunodepletion of proteins and discuss the use of immunodepletion and rescue experiments for functional analysis of components in the extracts...

....

..Our data are consistent with the existence of some limited self-organizing properties of the extreme ventral mesoderm...

..In addition, Xbra appears to inhibit cell migration by inhibiting adhesion to fibronectin. We propose that Xbra functions as a switch to keep cell migration and convergent extension as mutually exclusive behaviors during gastrulation...

..Based on labeling data and sequence analysis, we propose a model for the structure of separase, consisting of 26 ARM repeats, an unstructured region of 280 residues and two caspase-like domains, with securin binding to the ARM repeats...

..It also caused a cell division defect characterized by centrosome abnormalities and multipolar spindles. These findings implicate RASSF1A in the regulation of both APC-Cdc20 activity and mitotic progression...

..These findings represent a significantly revised view of Cdc42-signaling and shed light on the pathogenesis of Wiskott-Aldrich syndrome...

....

..Control of cell growth and cell shape are both fundamental to understanding many pathological conditions, in cancer and embryology. ..

..We ask how APC recognizes substrates and temporally distinguishes among them. Finally we examine the diversity of APC regulators and begin to characterize the possible role of APC outside the cell cycle. ..

..These studies are aimed at understanding actin regulation in a cellular context and the integration of actin regulation with other cellular functions. ..

..As such, it is a promising target for pharmacologic intervention. This proposal studies which proteins are signaled out for regulated degradation and on a molecular level how the particular choices are made. ..

..Control of cell growth and cell shape are both fundamental to understanding many pathological conditions, in cancer and embryology. ..

..Finally we propose to study two APC substrates with important biological effects: one involved in chromatid cohesion and the other affecting the growth of the brain in a human genetic disease. ..

..Our major approach here is to examine the early embryology of the acorn worm, Saccoglossus kowalevskii, and identify genes which in vertebrates play a major role in the Organizer. ..

..In the process, we will be investigating signaling pathways that may be use in many contexts of human biology. ..

..In aim 6 the activation of cdc2 by cyclin B and the identity and role of other activators and inhibitors will be studied. ..

..Specifically we will also be looking for clues for its role in generating aneuploidy and the reasons why it is oncogenic. ..

..Following experiments on the vertebrate homolog of cdc34, we plan to characterize its pathway of ubiquitin mediated degradation and potential substrates relative to the onset of DNA replication. ..