After studying at ENS Cachan (now Ecole Normale Supérieure Paris-Saclay, France), Arnaud Poterszman completed his PhD from Strasbourg University and joint the CNRS one year later. He holds a CNRS Research Director position and performs his studies in the Department of Integrated Structural Biology at IGBMC, Illkirch France. He has a dual expertise in Structural and Molecular biology with insights on expression technologies and sample preparation. He coordinates the protein expression module in Strasbourg for the European and French Infrastructures for Integrated Structural Biology INSTRUCT and FRISBI. His research is focused on eukaryotic multi-protein complexes involved in transcription regulation and DNA repair by nucleotide excision, particularly, the 10 subunits transcription/DNA repair factor TFIIH and its partners.
Molecular complexes of interacting proteins govern virtually all biological processes such as metabolism, cell signaling, DNA repair or gene expression. My interests focus on macromolecular machineries in the control of transcription regulation and maintenance of genome integrity using a combination of structural biology approaches and functional analysis.
My efforts have mainly targeted the TFIIH transcription/DNA repair factor. Identified as basal transcription factor (promoter opening and escape), TFIIH also plays a key role the DNA repair nucleotide excision repair (NER) which corrects UV induced lesions as well as DNA-damages that result from drugs used in chemotherapy such as cis-platin derivatives. TFIIH, a multi-protein complex composed of 10 subunits that harbours three enzymatic activities and can be resolved into two functional and structural entities: the 6-subunits core-TFIIH with the XPB helicase and the 3-subunits Cdk Activated Kinase complex (CAK). The XPD helicase which bridges core-TFIIH to CAK. Initially identified as basal transcription factor, TFIIH also participates in the transactivation of several hormone-dependent genes by phosphorylating nuclear receptors and plays a key role in nucleotide excision repair (NER) for damage verification, opening DNA at damaged sites and recruitment of additional repair factors. Mutations in the XPB, XPD or p8/Tfb5 result in rare diseases Xéroderma Pigmentosum (XP) or trichothiodystrophy (TTD).
Molecular architecture of human TFIIH and identification of functional modules differentially involved in transcription and DNA repair. The molecular architecture of TFIIH was analyzed using a combination of biochemical and biophysical experiments, leading to new insights into the organization of TFIIH and to atomic scale studies of several modules (1JKW, 1Z60, 1G25, 1PFJ, 2JNJ) and binary complexes (3DOM, 5O85) determined by X-ray crystallography or RMN. These finding highlighted the central roles of the p34, p44 and p62 subunits within TFIIH and lead to identification of functional modules differentially involved in transcription and DNA repair (Gervais et al. 2004; Radu et al. 2017).
Structural basis for Trichothiodystrophy. The structures of the yeast p8/TTD-A subunit from TFIIH isolated (Vitorino et al., 2007) as well as in complex with the p52 (Kainov et al., 2008) were also determined. The latter showed that p8/TTD-A protects a hydrophobic surface in p52 from solvent, providing a rationale for the influence of p8 in the stabilization of p52 and explaining why mutations that weaken p8–p52 interactions lead to a reduced intracellular TFIIH concentration and a defect in nucleotide-excision repair, a common feature of TTD cells.
Role of the XPD TFIIH subunit and regulation of its helicase activity. Biochemical analysis showed that the XPD ARCH domain specifically interacts with the CAK kinase complex and that association of XPD with CAK down regulates its helicase activity within TFIIH. Together with a detailed characterization of the C259Y variant (the unique mutation identified in a TTD patient) identified the ARCH domain of XPD as a platform for the recruitment of CAK and as a potential molecular switch that controls TFIIH composition and play a key role in the conversion of TFIIH from a factor active in transcription to a factor involved in DNA repair (Abdulrahman et al., 2013).
Technology developments for eukaryotic production of large multi-protein assemblies.
Sample preparation is a major limitation for multi protein complex research, particularly for applications in structural biology. Driven by the necessity to overcome this bottleneck, I have devoted part of my research activity on the developments of new tools to facilitate production and characterization of large and difficult multi protein complexes. These have focused on two main axis: (i) Recombinant production of proteins and multi protein complexes in insect cells using the baculovirus expression system (Abdulrahman et al., 2015; Berger and Poterszman, 2015) (BVES) and more recently (ii) isolation of endogenous complexes from CRISPR/Cas9 engineered mammalian cell lines.