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Small Molecule Disrupts G4-STAT1 Interaction and Synergizes with Olaparib to Drive Cancer Cell Death

ABSTRACT: Bloom syndrome protein (BLM), a RecQ family DNA helicase, is consistently overexpressed in multiple malignancies, yet its therapeutic potential remains largely unexplored. Herein, we focused on targeting the BLM promoter G-quadruplex (BLM-G4) to inhibit the BLM signaling pathway. We first characterized the parallel BLM-G4 in BLM promoter region. Subsequently, it is evidenced for the first time that BLM-G4 recruits phosphorylated STAT1 to activate BLM expression. Importantly, two natural alkaloids, berberine (BER) and coptisine (COP), compete with STAT1 for binding to BLM-G4, thereby significantly suppressing BLM expression in colon cancer cells. The BER/COP-BLM-G4 complex structures were determined using NMR experiments, which provide valuable insights for the rational design of next-generation BLM-G4-targeting ligands. Beyond BLM regulation, the conjoint analysis of genome-wide STAT1-CUT&Tag-seq, G4P-CUT&Tag-seq, and RNA-seq demonstrated STAT1 as a general G4-binding transcription factor and COP as a pan-genomic G4 stabilizer. Furthermore, BER/COP exhibited a pronounced synergistic effect with Olaparib in inducing colon cancer cell death by disrupting DNA repair pathways and intensifying DNA damage. Collectively, our findings reveal a novel epigenetic mechanism of BLM gene upregulation mediated by BLM-G4-STAT1 interaction and suggest that the combination therapy of G4 stabilizers with PARP inhibitors is a promising strategy for treating complex cancers.

ORGANISM(S): Homo sapiens

PROVIDER: GSE324248 | GEO | 2026/05/15

REPOSITORIES: GEO

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Project description:The human Werner and Bloom syndromes (WS and BS) are caused by deficiencies in the WRN and BLM RecQ helicases, respectively. WRN, BLM and their S. cerevisiae homologue Sgs1, are particularly active in vitro in unwinding G-quadruplex DNA (G4-DNA), a family of non-canonical nucleic acid structures formed by certain G-rich sequences. Recently, mRNA levels from loci containing potential G-quadruplex-forming sequences (PQS) were found to be preferentially altered in sgs1 mutants, suggesting that G4-DNA targeting by Sgs1 directly affects gene expression. Here, we extend these findings to human cells. Using microarrays to measure mRNAs obtained from human fibroblasts deficient for various RecQ family helicases, we observe significant associations between loci that are upregulated in WS or BS cells and loci that have PQS. No such PQS associations were observed for control expression datasets, however. Furthermore, upregulated genes in WS and BS showed no or dramatically reduced associations with sequences similar to PQS but that have considerably reduced potential to form intramolecular G4-DNA. These findings indicate that, like Sgs1, WRN and BLM can regulate transcription globally by targeting G4-DNA. Cell culture conditions and media Human fibroblast cell strains (WS: AG05229, AG12795, AG12797; BS: GM02932, GM03402, GM16891; RTS: AG18371, AG18375, AG05013; Normal/Wild-type: AG04054, AG06310, AG09975) were obtained from the Coriell Repository (Camden, NJ), from donors matched for gender and of similar ages, and were at similar passage levels. Cells were cultured in MEM supplemented with Earle’s salts, 20% fetal bovine serum, 1x penicillin/streptomycin, and 1x fungizone in 3% O2 at 37oC and harvested for RNA extraction during active growth and at ~ 80% confluence. GeneChip microarray expression Total RNA from the 12 fibroblast cell strains was isolated by extraction with TRIzol (Invitrogen) and purified using the RNeasy system (Qiagen). Total RNA was amplified by in vitro transcription using the Ovation RNA Amplification System V2 (NuGen). The resultant cDNA was fragmented and labeled using the FL-Ovation cDNA Biotin Module V2 (NuGen), and then purified using QIAquick columns (Qiagen), as specified by the Ovation System manual. Labeled probe was hybridized to Affymetrix U133A 2.0 GeneChips, and ultimately scanned using an Axon GenePix array scanner. Statistical analysis of microarray expression experiment The output files were normalized by Robust Multiarray Average (RMA), using the R package GCRMA and gene expression levels were log2-transformed.

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Small Molecule Disrupts G4-STAT1 Interaction and Synergizes with Olaparib to Drive Cancer Cell Death

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