HLTF Prevents G4 Accumulation and Promotes G4-induced Fork Slowing to Maintain Genome Stability
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PROVIDER: PRJNA1041318 | ENA |
REPOSITORIES: ENA
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Project description:G-quadruplexes (G4s) form throughout the genome and influence important cellular processes, but their deregulation can challenge DNA replication fork progression and threaten genome stability. Here, we demonstrate an unexpected, dual role for the dsDNA translocase HLTF in G4 metabolism. First, we find that HLTF is enriched at G4s in the human genome and suppresses G4 accumulation throughout the cell cycle using its ATPase activity. This function of HLTF affects telomere maintenance by restricting alternative lengthening of telomeres, a process stimulated by G4s. We also show that HLTF and MSH2, a mismatch repair factor that binds G4s, act in independent pathways to suppress G4s and to promote resistance to G4 stabilization. In a second, distinct role, HLTF restrains DNA synthesis upon G4 stabilization by suppressing PrimPol-dependent repriming. Together, the dual functions of HLTF in the G4 response prevent DNA damage and potentially mutagenic replication to safeguard genome stability.
2024-08-13 | GSE247967 | GEO
Project description:Regions of DNA with the potential to form secondary structure pose a frequent and significant impediment to DNA replication that must be actively countered by cells in order to preserve genetic and epigenetic integrity. The fork protection complex (FPC), a conserved group of replisome-associated proteins, comprising Timeless, plays an important role in maintaining efficient replisome function. A previously unappreciated DNA binding domain in the C terminus of Timeless, which exhibits specificity towards G4 structures, acts in collaboration with the DDX11 helicase to ensure replication of G4 structures in vivo and maintenance of genetic and epigenetic stability. Using RNA-seq experiments, we show that (i) Timeless and DDX11 share common gene targets, (ii) the promoter of Timeless- and DDX11-dependent genes are enriched in G4 structures in the vicinity of their promoter and (iii) both Timeless and DDX11 share a common set of gene targets with the FANCJ helicase known to maintain epigenetic stability in the vicinity of G4 structures.
2020-07-01 | GSE139256 | GEO
Project description:The fork protection complex promotes symmetric histone recycling to maintain heterochromatin
| PRJNA1006318 | ENA
Project description:Background G-quadruplexes (G4s) are stable non-canonical DNA secondary structures consisting of stacked arrays of four guanines, each held together by Hoogsteen hydrogen bonds. Sequences with the ability to form these structures in vitro, G4 motifs, are found throughout bacterial and eukaryotic genomes. The budding yeast Pif1 DNA helicase, as well as several bacterial Pif1 family helicases, unwind G4 structures robustly in vitro and suppress G4-induced DNA damage in S. cerevisiae in vivo. Results We determined the genomic distribution and evolutionary conservation of G4 motifs in four fission yeast species and investigated the relationship between G4 motifs and Pfh1, the sole S. pombe Pif1 family helicase. Using chromatin immunoprecipitation combined with deep sequencing, we found that many G4 motifs in the S. pombe genome were associated with Pfh1. Cells depleted of Pfh1 had increased fork pausing and DNA damage near G4 motifs, as indicated by high DNA polymerase occupancy and phosphorylated histone H2A, respectively. In general, G4 motifs were underrepresented in genes. However, Pfh1-associated G4 motifs were located on the transcribed strand of highly transcribed genes significantly more often than expected, suggesting that Pfh1 has a function in replication or transcription at these sites. Conclusions In the absence of functional Pfh1, unresolved G4 structures cause fork pausing and DNA damage of the sort associated with human tumors.
2014-12-03 | GSE59178 | GEO
Project description:Replication forks temporarily or terminally pause at hundreds of hard-to-replicate regions around the genome. A conserved pair of budding yeast replisome components Tof1-Csm3 (fission yeast Swi1-Swi3 and human TIMELESS-TIPIN) acts as a ‘molecular brake’ and promotes fork slowdown at proteinaceous replication fork barriers (RFBs), while the accessory helicase Rrm3 assists the replisome in removing protein obstacles. Here we show that Tof1-Csm3 complex promotes fork pausing independently of Rrm3 helicase by recruiting topoisomerase I (Top1) to the replisome. Topoisomerase II (Top2) partially compensates for the pausing decrease in cells when Top1 is lost from the replisome. The C-terminus of Tof1 is specifically required for Top1 recruitment to the replisome and fork pausing but not for DNA replication checkpoint (DRC) activation. We propose that forks pause at proteinaceous RFBs through a ‘sTOP’ mechanism (‘slowing down with TOPoisomerases I-II’), which we show also contributes to protecting cells from topoisomerase-blocking agents.
2019-11-07 | GSE140034 | GEO
Project description:Geobacillus sp. G4 strain:G4 Genome sequencing
| PRJNA1124973 | ENA
Project description:The fork protection complex promotes symmetric histone recycling to maintain heterochromatin [SCAR-seq]
| PRJNA1006322 | ENA
Project description:The fork protection complex promotes symmetric histone recycling to maintain heterochromatin [ChIP-Seq]
| PRJNA1006042 | ENA
Project description:The helicase-like transcription factor (HLTF) gene – a tumor suppressor in human colorectal cancer (CRC) - is regulated by alternative splicing and promoter hypermethylation. The detection of hypermethylated HLTF DNA in fecal occult blood tests is an indicator of disease recurrence and poor survival. Hltf-deficiency in the ApcMin/+ mouse strain increased the formation of intestinal adenocarcinoma with a high incidence of gross chromosomal instabilities. To investigate Hltf-deletion effects in CRC without cross-breeding into a tumorigenic strain, Hltf-deletion was studied in mice treated with the carcinogen azoxymethane (AOM) and the proinflammatory agent dextran sulfate (DSS). Hltf-deletion resulted in weight loss beginning at treatment week 6, and poor survival (Kaplan-Meier survival plot). Hltf-deletion increased tumor multiplicity compared to controls, and dramatically shifted the topographic distribution of lesions into the rectum. Differential isoform expression analysis of lesions from control mice revealed both the truncated isoform that lacks a DNA-repair domain and the full length isoform capable of DNA damage repair are present (3:1.8 ratio) during adenocarcinoma formation. iPathwayGuide identified 51 dynamically regulated genes of 10,967 total genes with measured expression. Oxidative Phosphorylation (Kegg: 00190), the top biological pathway (p=0.006; p value correction: Bonferroni) perturbed by Hltf-deletion, resulted from increased transcription of Atp5e, Cox7c, Uqcr11, Ndufa4 and Ndufb6 genes, concomitant with increased endogenous levels of ATP (p=0.0176). Upregulation of gene expression, as validated with qRT-PCR, was accompanied by a stable mtDNA/nDNA ratio. This is the first study to show Hltf-deletion in an inflammation-associated CRC model elevates mitochondrial bioenergetics. The distal shift in tumorigenesis indicates the detection of hypermethylated HLTF DNA in human stool samples might be a prognostic biomarker for distal (left-sided) colorectal cancer rather than proximal (right-sided) colon cancer.
2019-06-18 | GSE132814 | GEO
Project description:Nucleotide excision repair (NER) counteracts the onset of cancer and aging by removing helix-distorting DNA lesions via a ‘cut-and-patch’-type reaction. The regulatory mechanisms that drive NER through its successive damage recognition, verification, incision and gap restoration reaction steps remain elusive. Here we show that the RAD5-related translocase HLTF facilitates repair through active eviction of incised damaged DNA together with associated repair proteins. Our data shows a dual incision-dependent recruitment of HLTF to the NER incision complex, mediated by HLTF’s HIRAN domain that binds 3’-OH single-stranded DNA ends. HLTF’s translocase motor subsequently promotes dissociation of incised oligonucleotides together with members of the stably damage-bound incision complex to allow efficient PCNA loading and initiation of repair synthesis. Our findings uncover HLTF as an important NER factor that actively evicts DNA damage, thereby providing an additional quality control by coordinating the transition between the excision and DNA synthesis steps to safeguard genome integrity.
2023-05-10 | PXD031243 | Pride