Biology subjects

Rzechorzek, N. J.

Publications and source records attributed to Rzechorzek, N. J..

4 recordsLinked to original sources

bioRxiv2021

Structural basis for the interaction of SARS-CoV-2 virulence factor nsp1 with Pol α - Primase

The molecular mechanisms that drive the infection by the SARS-CoV-2 coronavirus - the causative agent of the COVID-19 (Coronavirus disease-2019) pandemic - are under intense current scrutiny, to understand how the virus operates and to uncover ways in which the disease can be prevented or alleviated. Recent cell-based analyses of SARS-CoV-2 protein - protein interactions have mapped the human proteins targeted by the virus. The DNA polymerase - primase complex or primosome - responsible for initiating DNA synthesis in genomic duplication - was identified as a target of nsp1 (non structural protein 1), a major virulence factor in the SARS-CoV-2 infection. Here, we report the biochemical characterisation of the interaction between nsp1 and the primosome and the cryoEM structure of the primosome - nsp1 complex. Our data provide a structural basis for the reported interaction between the primosome and nsp1. They suggest that Pol - primase plays a part in the immune response to the viral infection, and that its targeting by SARS-CoV-2 aims to interfere with such function.

biophysics↗

bioRxiv2021

Structural basis for the coiled-coil architecture of human CtIP

The DNA repair factor CtIP has a critical function in Double-Strand Break (DSB) repair by Homologous Recombination, promoting the assembly of the repair apparatus at DNA ends and participating in DNA-end resection. However, the molecular mechanisms of CtIP function in DSB repair remain unclear. Here we present an atomic model for the three-dimensional architecture of human CtIP, derived from a multi-disciplinary approach that includes X-ray crystallography, Small-angle X-ray Scattering (SAXS) and Diffracted X-ray Tracking (DXT). Our data show that CtIP adopts an extended dimer-of-dimers structure, in agreement with a role in bridging distant sites on chromosomal DNA during recombinational repair. The zinc-binding motif in CtIPs N-terminus alters dynamically the coiled coil structure, with functional implications for the long-range interactions of CtIP with DNA. Our results provide a structural basis for the three-dimensional arrangement of chains in the CtIP tetramer, a key aspect of CtIP function in DNA DSB repair.

biophysics↗

bioRxiv2020

CryoEM structures of human CMG - ATPγS - DNA and CMG - AND-1 complexes

DNA unwinding in eukaryotic replication is performed by the Cdc45-MCM-GINS (CMG) helicase. Although the CMG architecture has been elucidated, its mechanism of DNA unwinding and replisome interactions remain poorly understood. Here we report the cryoEM structure at 3.3 [A] of human CMG bound to fork DNA and the ATP-analogue ATP{gamma}S. Eleven nucleotides of single-stranded (ss) DNA are bound within the C-tier of MCM2-7 AAA+ ATPase domains. All MCM subunits contact DNA, from MCM2 at the 5'-end to MCM5 at the 3'-end of the DNA spiral, but only MCM6, 4, 7 and 3 make a full set of interactions. DNA binding correlates with nucleotide occupancy: five MCM subunits are bound to either ATP{gamma}S or ADP, whereas the apo MCM2-5 interface remains open. We further report the cryoEM structure of human CMG bound to the replisome hub AND-1 (CMGA). The AND-1 trimer uses one {beta}-propeller domain of its trimerisation region to dock onto the side of the helicase assembly formed by Cdc45 and GINS. In the resulting CMGA architecture, the AND-1 trimer is closely positioned to the fork DNA while its CIP (Ctf4-interacting peptide)-binding helical domains remain available to recruit partner proteins.

biochemistry↗

bioRxiv2019

Structural basis for inhibition of human primase by arabinofuranosyl nucleoside analogues Fludarabine and Vidarabine

Nucleoside analogues are widely used in clinical practice as chemotherapy drugs. Arabinose nucleoside derivatives such as Fludarabine are effective in the treatment of patients with acute and chronic leukemias and non-Hodgkin lymphomas. Although nucleoside analogues are generally known to function by inhibiting DNA synthesis in rapidly proliferating cells, the identity of their in vivo targets and mechanism of action are often not known in molecular detail. Here we provide a structural basis for inhibition by arabinose nucleotides of human primase, the DNA-dependent RNA polymerase responsible for initiation of DNA synthesis in DNA replication. Our data suggest ways in which the chemical structure of Fludarabine could be modified to improve its specificity and affinity towards primase, possibly leading to less toxic and more effective therapeutic agents.

biochemistry↗