Kinetochores are proteinaceous assemblies that mediate the interaction of chromosomes with the mitotic spindle. The 180 kDa Ndc80 complex is a direct point of contact between kinetochores and microtubules. Its four subunits contain coiled coils and form an elongated rod structure with functional globular domains at either end. We crystallized an engineered "bonsai" Ndc80 complex containing a shortened rod domain but retaining the globular domains required for kinetochore localization and microtubule binding. The structure reveals a microtubule-binding interface containing a pair of tightly interacting calponin-homology (CH) domains with a previously unknown arrangement. The interaction with microtubules is cooperative and predominantly electrostatic. It involves positive charges in the CH domains and in the N-terminal tail of the Ndc80 subunit and negative charges in tubulin C-terminal tails and is regulated by the Aurora B kinase. We discuss our results with reference to current models of kinetochore-microtubule attachment and centromere organization.

Cell patterning is an important tool for organizing cells in surfaces and to reproduce in a simple way the tissue hierarchy and complexity of pluri-cellular life. The control of cell growth, proliferation and differentiation on solid surfaces is consequently important for prosthetics, biosensors, cell-based arrays, stem cell therapy and cell-based drug discovery concepts. We present a new electron beam lithography method for the direct and simultaneous fabrication of sub-micron topographical and chemical patterns, on a biocompatible and biodegradable PAA hydrogel. The localized e-beam modification of a hydrogel surface makes the pattern able to adsorb proteins in contrast with the anti-fouling surface. By also exploiting the selective attachment, growth and differentiation of PC12 cells, we fabricated a neural network of single cells connected by neuritis extending along microchannels. E-beam microlithography on PAA hydrogels opens up the opportunity of producing multifunctional microdevices incorporating complex topographies, allowing precise control of the growth and organization of individual cells.

e Epstein-Barr virus (EBV) establishes a life-long latent infection in humans. In proliferating latently infected cells, EBV genomes persist as multiple episomes that undergo one DNA replication event per cell cycle and remain attached to the mitotic chromosomes. EBV nuclear antigen 1 (EBNA-1) binding to the episome and cellular genome is essential to ensure proper episome replication and segregation. However, the nature and regulation of EBNA-1 interaction with chromatin has not been clearly elucidated. This activity has been suggested to involve EBNA-1 binding to DNA, duplex RNA, and/or proteins. EBNA-1 binding protein 2 (EBP2), a nucleolar protein, has been proposed to act as a docking protein for EBNA-1 on mitotic chromosomes. However, there is no direct evidence thus far for EBP2 being associated with EBNA-1 during mitosis. By combining video microscopy and Förster resonance energy transfer (FRET) microscopy, we demonstrate here for the first time that EBNA-1 and EBP2 interact in the nucleoplasm, as well as in the nucleoli during interphase. However, in strong contrast to the current proposed model, we were unable to observe any interaction between EBNA-1 and EBP2 on mitotic chromosomes. We also performed a yeast doublehybrid screening, followed by a FRET analysis, that led us to identify HMGB2 (high-mobility group box 2), a well-known chromatin component, as a new partner for EBNA-1 on chromatin during interphase and mitosis. Although the depletion of HMGB2 partly altered EBNA-1 association with chromatin in HeLa cells during interphase and mitosis, it did not significantly impact the maintenance of EBV episomes in Raji cells.

Abstract. We briefly introduce the notion of Semantically Enhanced Library Languages, SELL, as a practical and economical alternative to special-purpose programming languages for high-performance computing. Then we describe the Pivot infrastructure for program analysis and transformation that is our main tool for supporting SELL. Finally, we outline how the IPR (The Pivot's Internal Program Representation) can be used to represent central notions of high-performance computing, such as parallelizable array operations. Our focus is on a broad exposition of ideas, rather than technical details 1 . Languages and librariesFor ease of programming, portability, and acceptable performance, we design and implement special-purpose programming languages for high-performance computing [15]. Alternatively, we can use a Semantically Enhanced Library Language. A SELL is a language created by extending a programming language (usually a popular general-purpose programming language) with a library providing the desired added functionality and then using a tool to provide the desired semantic guarantees needed to reach a goal (often a higher level semantics, absence of certain kinds of errors, or library-specific optimizations) [12]. This paper focuses on a tool, The Pivot, being developed to support SELLs in ISO C++ [11,5] and its application to High-Performance Computing. A brief overview of the PivotThe Pivot is a general framework for the analysis and transformation of C++ programs. It is designed to handle the complete ISO C++, especially more advanced uses of templates and including some proposed C++0x features. It is compiler independent. The central part of the Pivot is a fully typed abstract syntax tree called IPR (Internal Program Representation).There are lots of (more than 20) tools for static analysis and transformation of C++ programs, e.g. [7,2,8,6]. However, few -if any -handle all of ISO 1 This is the "cut" or "abbreviated" version of this paper. For a full version, see

Front Cover: The cover image shows the design of neural networks or cellular microenvironments based on an original hydrogel microfabrication process. Polyamidoamine hydrogels patterned by an electron beam can adsorb proteins as a function of exposure dose. Individual PC12 cells grow in microfabricated wells showing neurite guidance along channels, thus obtaining interconnected neural circuits. Further details can be found in the full paper by G. Dos Reis, F. Fenili, A. Gianfelice, G. Bongiorno, D. Marchesi, P. E. Scopelliti, A. Borgonovo, A. Podestà, M. Indrieri, E. Ranucci, P. Ferruti, C. Lenardi,* and P. Milani* .

Object layout -the concrete in-memory representation of objects -raises many delicate issues in the case of the C++ language, owing in particular to multiple inheritance, C compatibility and separate compilation. This paper formalizes a family of C++ object layout schemes and mechanically proves their correctness against the operational semantics for multiple inheritance of Wasserrab et al. This formalization is flexible enough to account for spacesaving techniques such as empty base class optimization and tailpadding optimization. As an application, we obtain the first formal correctness proofs for realistic, optimized object layout algorithms, including one based on the popular "common vendor" Itanium C++ application binary interface. This work provides semantic foundations to discover and justify new layout optimizations; it is also a first step towards the verification of a C++ compiler frontend.

Selecting operations based on the run-time type of an object is key to many object-oriented and functional programming techniques. We present a technique for implementing open and efficient type switching on hierarchical extensible data types. The technique is general and copes well with C++ multiple inheritance.To simplify experimentation and gain realistic performance using production-quality compilers and tool chains, we implement a type switch construct as an ISO C++11 library, called Mach71 . This library-only implementation provides concise notation and outperforms the visitor design pattern, commonly used for case analysis on types in objectoriented programming. For closed sets of types, its performance roughly equals equivalent code in functional languages, such as OCaml and Haskell. The type-switching code is easier to use and is more expressive than hand-coded visitors are. The library is non-intrusive and circumvents most of the extensibility restrictions typical of the visitor design pattern. It was motivated by applications involving large, typed, abstract syntax trees.

We present a formal operational semantics and its Coq mechanization for the C++ object model, featuring object construction and destruction, shared and repeated multiple inheritance, and virtual function call dispatch. These are key C++ language features for high-level system programming, in particular for predictable and reliable resource management. This paper is the first to present a formal mechanized account of the metatheory of construction and destruction in C++, and applications to popular programming techniques such as "resource acquisition is initialization". We also report on irregularities and apparent contradictions in the ISO C++03 and C++11 standards.