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DNA ligase 1 (LIG1) finalizes eukaryotic nuclear DNA synthesis by sealing Okazaki fragments using DNA end-joining reactions. Here the authors, by studying an engineered low-fidelity LIG1, reveal that LIG1 is a highly accurate DNA ligase in vivo.

Genome-wide analyses of S. cerevisiae replisome mobility reveal overlapping roles of Pif1 and Rrm3 helicases in alleviating replication-fork arrest at tRNA genes.

PCNA–PAF15 has a key role in determining replisome dynamics during genome replication and protecting against genome instability.

Pol δ bound to the proliferating cell nuclear antigen (PCNA) replicates the lagging strand in eukaryotes and cooperates with flap endonuclease 1 (FEN1) to process the Okazaki fragments for their ligation. Here, the authors present a Cryo-EM structure of the human 4-subunit Pol δ bound to DNA and PCNA in a replicating state with an incoming nucleotide in the active site.

Telomeres are endogenous cellular targets of DNA ADP-ribosylation (DNA-ADPr). TARG1-regulated DNA-ADPr is coupled to lagging telomere DNA strand synthesis, and persistent DNA-ADPr, due to TARG1 deficiency, leads to telomere shortening and fragility.

CFAP20 has a key role in rescuing RNA polymerase II complexes that have arrested during DNA transcription, limiting the accumulation of R-loops and preventing collisions between the transcription and replication machinery.

Instability of (CTG)•(CAG) repeats in microsatellite DNA has been linked to numerous neurological diseases. Probing trinucleotide repeat structures using engineered zinc-finger nucleases provides evidence that DNA hairpins form in vivo and are linked to replication-dependent genomic instability.

In the absence of RNase H2, ribonucleotides incorporated during DNA replication can be processed by Top1. This activity is directed to the nascent leading strand, because gaps in the lagging strand would limit torsional tension.

DNA is replicated by a replisome containing two DNA polymerase molecules, one of which copies the leading-strand template in a continuous manner while the second copies the lagging-strand template in a discontinuous manner; however, the two strands are synthesized at the same net rate. RNA primers are now shown to be made as DNA is being synthesized and then passed on to the polymerase; to allow for this transfer, the lagging-strand polymerase has a faster rate.

Genetic and genomic analyses show that S. cerevisiae DNA polymerase δ extrinsically proofreads for errors by polymerase ε and itself, and demonstrate that the symmetry of replication fidelity is achieved via coordinated efforts of intrinsic and extrinsic proofreading and DNA mismatch repair.

A large cross-population atlas of gene–environment interactions reveals how age, sex and lifestyle shape genetic effects, heritability, prediction accuracy and disease biology, with implications for personalized medicine and drug development.

The current model for B-family DNA polymerases in archaea is one of single-subunit enzymes in contrast to the multi-subunit complexes in eukaryotes. Here the authors show that PolB1 fromSulfolobus solfataricusexists as a heterotrimeric complex in cell extracts.

Combinatorial CRISPRi screening was used to map genetic interactions in DNA damage response pathways, revealing known and new connections, including the roles of WDR48 and USP1 in preventing under-replication and SMARCAL1 and FANCM in remodelling persistent cruciform DNA structures.

The emRiboSeq sequencing method is used to track polymerase activity genome-wide in vivo; despite Okazaki fragment processing, DNA synthesized by error-prone polymerase-α (Pol-α) is retained in vivo and comprises ∼1.5% of the genome, establishing Pol-α as an important source of genomic variability and providing a mechanism for site-specific variation in nucleotide substitution rates.

Flap Endonuclease 1 is a DNA replication and repair enzyme indispensable for maintaining genomic stability. Here the authors provide mechanistic details on how FEN1 selects for 5′-flaps and promotes catalysis to avoid large-scale repeat expansion by a process termed ‘phosphate steering’.

A method for single-molecule imaging at high protein concentrations is presented and demonstrated in the context of DNA replication in cell extracts.

The termination of DNA replication involves convergence of replication forks, the completion of DNA synthesis, replisome disassembly and the decatenation of daughter DNA molecules. Recent discoveries illustrate how replisome disassembly in eukaryotes is controlled by E3 ubiquitin ligases and how this activity is regulated to avoid genome instability.

Escherichia coli SSB enriches Pol IV polymerase at lesion-stalled replication forks, promoting translesion synthesis. Loss of this enrichment increases repriming of DNA synthesis, revealing a pivotal role of SSB in the pathway choice of stalled replication forks.

KCTD10 interacts with the DNA replication machinery and the RNA polymerase complex, inducing ubiquitination and removal of the transcription machinery in the event of co-directional transcription–replication conflicts.

HydEn-seq, a new sequencing method that maps the distribution of ribonucleotides misincorporated by low-fidelity DNA polymerases in budding yeast, reveals unexpected strand-specific replication patterns in both nuclear and mitochondrial genomes.

DNA ligase 1 finalizes nuclear DNA replication by accurately sealing nicks generated during Okazaki Fragment Maturation. Here, Williams et al employ a low fidelity DNA ligase 1 variant to study mutation rates and specificity across the yeast genome

EXO1 performs multiple roles in DNA replication and DNA damage repair (DDR), but its role in DDR-deficient cancers remains unclear. Here, the authors find EXO1 loss as synthetic lethal with many DDR genes involved in various cancers, including genes from Fanconi Anaemia pathway, BRCA1-A complex, and spliceosome factor ZRSR2; such interactions represent potential clinical targets.

Loss-of-function mutations in EP300/KAT3B and CBP/KAT3A have been implicated in the pathogenesis of cancer. Here, the authors reveal that the EP300 protein has a role in mediating replication fork protection at sites of replication stalling and show that EP300-mutated cells recapitulate features of BRCA-deficient cancers.

DNA sliding clamps are ring-shaped proteins that encircle DNA and harbour polymerases and other factors that promote processive DNA replication. Here the authors use X-ray crystallography, NMR and MD simulations to propose a model for a PCNA sliding mechanism that relies on short-lived polar interactions.

Mammalian DNA replication relies on various helicases and nucleases to ensure accurate genetic duplication, but how these enzymes are properly directed is unclear. Here, the authors identify USP50 as a key protein for promoting ongoing replication, restarting stalled forks, maintaining telomeres, and ensuring cell survival.

The authors develop an EM-based method to directly visualize R-loops. Applying this method to transcription-replication conflicts in human and bacterial cells, they show that DNA:RNA hybrids accumulate primarily behind replication forks, and are linked to fork slowing and fork reversal.

The influence of chromatin structure on the DNA replication programme is reciprocated by replication-coupled mechanisms that re-establish chromatin on newly formed DNA. The tight coupling of these processes is essential for promoting integrity of the genome and epigenome, with possible implications for ageing and cancer.

Japan's hidebound university system is being reformed.

The electron transfer from aluminum to hematite in a thermite reaction is investigated here using femtosecond extreme-ultraviolet spectroscopy, offering insights into charge flow in energetic materials and laying the basis for studying chemical reactions in the solid state at the femtosecond timescale.

Barriers to DNA replication are potent sources of genome instability. Here, the authors provide a mechanistic model for how a single persistent G-quadruplex structure generates multiple substrates for polymerase theta-mediated end-joining, thus causing multiple deletions during animal development.

Structure-specific endonucleases (SSEs) function in concert with other DNA-remodelling enzymes and cell cycle control machineries in processes such as DNA adduct repair, Holliday junction processing and the response to replication stress. As SSEs have specificity for DNA structures rather than sequence, tight regulation of their activity is important to ensure genome stability.

Tissue regeneration is of great interest; however the number of times a given tissue can regenerate is unknown. Now, Eguchiet al. demonstrate that the lens of the Japanese newt—Cynops pyrrhogaster—can regenerate 18 times over a 16-year period, and that the new lenses are similar to those of control adult animals.

Ribonucleotides are incorporated into DNA by various mechanisms, including by DNA polymerases during replication. Such ribonucleotides may have physiological functions, but their presence is typically associated with diverse structural aberrations and interferes with fundamental processes, including DNA replication, repair and transcription. Thus, efficient mechanisms of ribonucleotide removal are key to maintaining genomic integrity and functionality.

The authors develop a system to erase DNA methylation at H19-DMR in mouse sperm. Despite loss, methylation partly recovers via H3K9me3 after fertilization, revealing partial intergenerational epigenetic inheritance.

In neural progenitor cells, recurrent DNA break clusters (RDCs) occur to genes crucial for brain function. Here the authors find that most RDCs emerge at long-traveling unidirectional replication forks, and often unrelated to R-loops.

A new 'metal mimic' mutagenesis approach that captures a T5 flap endonuclease complex with an intact DNA substrate provides structural evidence that the single-stranded 5′ flap generated by Okazaki-fragment synthesis threads through the flap endonuclease enzyme.

DNA replication of repetitive sequences was recreated in a test tube using purified components. DNA alone was sufficient to induce stalling. Both stalling and recovery were dictated by the capacity of DNA to fold into unusual secondary structures.