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Buckley, Ryan J. (2023) Biochemical and genetic analysis of Lhr, a mysterious helicase/glycosylase conserved across species. PhD thesis, University of Nottingham.

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Abstract

Changes to DNA structure frequently inhibit essential processes such as DNA replication. Overcoming replication blockage or collapse requires replication-coupled DNA repair enzymes that catalyse removal of aberrant DNA structures and chemically modified bases. The Lhr family of helicases are found throughout archaea, including in the Heimdall- and Nano- archaeota, and are present in several bacterial clades. This family can be divided into ‘Lhr-core’ and ‘Lhr-extended’ protein variants with the latter containing an as yet uncharacterised extended C-terminal domain.

Through genetic analysis we identified an expression phenotype of archaeal Lhr identical to the replication-coupled DNA repair enzymes Hel308 and RecQ and implicated bacterial Lhr in a novel mutation repair pathway and in overcoming oxidative stress through interaction with a Rad51 paralogue.

In vitro analysis demonstrated archaeal Lhr preferential targeting of replication fork structures through ATP-independent binding causing melting/distortion of the branch point. This allowed loading for directional translocation and unwinding through the ‘parental’ DNA strands. Characterisation of bacterial Lhr-CTD revealed a newly identified d-uracil DNA glycosylase activity, building an emerging story about the contribution of Lhr and its associated proteins in prokaryotic DNA repair. Further context is afforded through phylogenetic analysis of RecA/Rad51 family proteins revealing the emergence of protein sub-families.

Here we present a substantial breakthrough in the study of Lhr proteins, implicating them for direct involvement in replication-coupled repair and a wider role in base excision repair.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Bolt, Edward L. Soultanas, Panos
Keywords:	Lhr, DNA, Helicase, Glycosylase, DNA repair, DNA replication, Genetics, Biochemistry
Subjects:	Q Science > QR Microbiology > QR 75 Bacteria. Cyanobacteria
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID:	72474
Depositing User:	Buckley, Ryan
Date Deposited:	31 Jul 2023 04:40
Last Modified:	31 Jul 2023 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/72474

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