Biology subjects

Maman, J. D.

Publications and source records attributed to Maman, J. D..

4 recordsLinked to original sources

bioRxiv2025

Structural mechanism of strand exchange by the RAD51 filament.

Homologous Recombination (HR) preserves genomic stability by repairing double-strand DNA breaks and ensuring efficient DNA replication. Central to HR is the strand-exchange reaction taking place within the three-stranded synapsis wherein a RAD51 nucleoprotein filament binds to a donor DNA. Here we present the cryoEM structure of a displacement loop of human RAD51 that captures the synaptic state when the filament has become tightly bound to the donor DNA. The structure elucidates the mechanism of strand exchange by RAD51, including the filament engagement with the donor DNA, the strand invasion and pairing with the complementary sequence of the donor DNA, the capture of the non-complementary strand and the polarity of the strand-exchange reaction. Our findings provide fundamental mechanistic insights into the biochemical reaction of eukaryotic HR.

molecular biology↗

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↗

bioRxiv2019

Timeless couples G quadruplex detection with processing by DDX11 during DNA replication

Regions of the genome with the potential to form secondary structure pose a frequent and significant impediment to DNA replication and must be actively managed in order to preserve genetic and epigenetic integrity. The fork protection complex (FPC), a conserved group of replisome-associated proteins including Timeless, Tipin, and Claspin, plays an important role in maintaining efficient replisome activation, ensuring optimum fork rates, sister chromatid cohesion and checkpoint function. It also helps maintain the stability of sequences prone to secondary structure formation through an incompletely understood mechanism. Here, we report a previously unappreciated DNA binding domain in the C-terminus of Timeless, which exhibits specific binding to G quadruplex (G4) structures. We show that, in vivo, both the C-terminus of Timeless and the DDX11 helicase act collaboratively to ensure processive replication of G4 structures to prevent genetic and epigenetic instability.

molecular biology↗