Genetic, Biochemical, and Biophysical Methods for Studying FeS Proteins and Their Assembly.

International audienceFeS clusters containing proteins are structurally and functionally diverse and present in most organisms. Our understanding of FeS cluster production and insertion into polypeptides has benefited from collaborative efforts between in vitro and in vivo studies. The former allows a detailed description of FeS-containing protein and a deep understanding of the molecular mechanisms catalyzing FeS cluster assembly. The second allows to include metabolic and environmental constraints within the analysis of FeS homeostasis. The interplay and the cross talk between the two approaches have been a key strategy to reach a multileveled integrated understanding of FeS cluster homeostasis. In this chapter, we describe the genetic and biochemical/biophysical strategies that were used in the field of FeS cluster biogenesis, with the aim of providing the reader with a critical view of both approaches. In addition to the description of classic tricks and a series of recommendations, we will also discuss models as well as spectroscopic techniques useful to characterize FeS clusters such as UV-visible, Mössbauer, electronic paramagnetic resonance, resonance Raman, circular dichroism, and nuclear magnetic resonance

Nucleolin is a histone chaperone with FACT-like activity and assists remodeling of nucleosomes

Remodeling machines play an essential role in the control of gene expression, but how their activity is regulated is not known. Here we report that the nuclear protein nucleolin possesses a histone chaperone activity and that this factor greatly enhances the activity of the chromatin remodeling machineries SWI/SNF and ACF. Interestingly, nucleolin is able to induce the remodeling by SWI/SNF of macroH2A, but not of H2ABbd nucleosomes, which are otherwise resistant to remodeling. This new histone chaperone promotes the destabilization of the histone octamer, helping the dissociation of a H2A–H2B dimer, and stimulates the SWI/SNF-mediated transfer of H2A–H2B dimers. Furthermore, nucleolin facilitates transcription through the nucleosome, which is reminiscent of the activity of the FACT complex. This work defines new functions for histone chaperones in chromatin remodeling and regulation of transcription and explains how nucleolin could act on transcription

Implementation Failures as Learning Pathologies

This is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this recordIn many ways, the study of implementation is the study of policy failure. After all, scholarly preoccupation with the causes of policy pathologies motivated the first wave of implementation studies in the post-war decades (Derthick 1972; Pressman and Wildavsky 1973). Examination of policy learning has followed a similar trajectory. The first (and now classic) studies linking learning and policy change were central to the serious efforts to create a systematic approach to policy sciences (Deutsch 1966; Heclo 1974; Lindblom 1965). Recent developments re-appraising policy learning, and in particular spotlighting its varieties and its limitations, enable a clearer connection with implementation fiascos (Howlett 2012; Dunlop and Radaelli 2013, 2018). New conceptualisations of policy learning point to the importance of scope conditions which render learning deep or shallow, functional or dysfunctional (Dunlop 2017). In this chapter, the implementation failure-policy learning nexus is explored at three analytical levels: micro level of individual policy actors; meso level of groups and organisational bodies; and finally, the macro, systemic level