Lsh Mediated RNA Polymerase II Stalling at HoxC6 and HoxC8 Involves DNA Methylation

DNA cytosine methylation is an important epigenetic mechanism that is involved in transcriptional silencing of developmental genes. Several molecular pathways have been described that interfere with Pol II initiation, but at individual genes the molecular mechanism of repression remains uncertain. Here, we study the molecular mechanism of transcriptional regulation at Hox genes in dependence of the epigenetic regulator Lsh that controls CpG methylation at selected Hox genes. Wild type cells show a nucleosomal deprived region around the transcriptional start site at methylated Hox genes and mediate gene silencing via Pol II stalling. Hypomethylation in Lsh−/− cells is associated with efficient transcriptional elongation and splicing, in part mediated by the chromodomain protein Chd1. Dynamic modulation of DNA methylation in Lsh−/− and wild type cells demonstrates that catalytically active DNA methyltransferase activity is required for Pol II stalling. Taken together, the data suggests that DNA methylation can be compatible with Pol II binding at selected genes and Pol II stalling can act as alternate mechanism to explain transcriptional silencing associated with DNA methylation

IKKα inactivation promotes Kras-initiated lung adenocarcinoma development through disrupting major redox regulatory pathways.

Lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC) are two distinct and predominant types of human lung cancer. IκB kinase α (IKKα) has been shown to suppress lung SCC development, but its role in ADC is unknown. We found inactivating mutations and homologous or hemizygous deletions in the CHUK locus, which encodes IKKα, in human lung ADCs. The CHUK deletions significantly reduced the survival time of patients with lung ADCs harboring KRAS mutations. In mice, lung-specific Ikkα ablation (IkkαΔLu ) induces spontaneous ADCs and promotes KrasG12D-initiated ADC development, accompanied by increased cell proliferation, decreased cell senescence, and reactive oxygen species (ROS) accumulation. IKKα deletion up-regulates NOX2 and down-regulates NRF2, leading to ROS accumulation and blockade of cell senescence induction, which together accelerate ADC development. Pharmacologic inhibition of NADPH oxidase or ROS impairs KrasG12D-mediated ADC development in IkkαΔLu mice. Therefore, IKKα modulates lung ADC development by controlling redox regulatory pathways. This study demonstrates that IKKα functions as a suppressor of lung ADC in human and mice through a unique mechanism that regulates tumor cell-associated ROS metabolism

Oncostatic actions of melatonin on tumor cell growth in the LNCaP model of human prostate cancer

published_or_final_versionPhysiologyDoctoralDoctor of Philosoph

Abiotic niche divergence of hybrid species from their progenitors

Funding information: This work was equally supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (grant XDB31000000), the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502), the National Key Research and Development Program of China (2017YFC0505203), the National Natural Science Foundation of China (31590821), and the Fundamental Research Funds for the Central Universities (2020SCUNL207).Although more frequently discussed recently than previously, the role of ecology in homoploid hybrid and allopolyploid speciation has not been subjected to comparative analysis. We examined abiotic niche divergence of 22 assumed homoploid hybrid species and 60 allopolyploid species from that of their progenitors. Ecological niche modeling was employed in an analysis of each species’ fundamental niche, and ordination methods were used in an analysis of realized niches. Both analyses utilized 100,000 georeferenced records. From estimates of niche overlap and niche breadth, we identified for both types of hybrid species four niche divergence patterns: niche novelty, niche contraction, niche intermediacy, and niche expansion. Niche shifts involving niche novelty were common and considered likely to play an important role in the establishment of both types of hybrid species, although more so for homoploid hybrid species than for allopolyploid species. Approximately 70% of homoploid hybrid species versus 37% of allopolyploid species showed shifts in the fundamental niche from their parents, and ∼86% versus ∼52%, respectively, exhibited shifts in the realized niche. Climate was shown to contribute more than soil and landform to niche shifts in both types of hybrid species. Overall, our results highlight the significance of abiotic niche divergence for hybrid speciation, especially without genome duplication.Publisher PDFPeer reviewe

The miR 495-UBE2C-ABCG2/ERCC1 axis reverses cisplatin resistance by downregulating drug resistance genes in cisplatin-resistant non-small cell lung cancer cellsResearch in context

Cisplatin (DDP) resistance has become the leading cause of mortality in non-small cell lung cancer (NSCLC). miRNA dysregulation significantly contributes to tumor progression. In this study, we found that miR-495 was significantly downregulated in lung cancer tissue specimens. This study aimed to elucidate the functions, direct target genes, and molecular mechanisms of miR-495 in lung cancer. miR-495 downregulated its substrate UBE2C through direct interaction with UBE2C 3′- untranslated region. UBE2C is a proto-oncogene activated in lung cancer; however, its role in chemotherapeutic resistance is unclear. Herein, UBE2C expression levels were higher in DDP-resistant NSCLC cells; this was associated with the proliferation, invasion, and DDP resistance in induced cisplatin-resistant NSCLC cells. Furthermore, epithelial–mesenchymal transitions (EMT) contributed to DDP resistance. Moreover, UBE2C knockdown downregulated vimentin. In contrast, E-cadherin was upregulated. Importantly, miR-495 and UBE2C were associated with cisplatin resistance. We attempted to evaluate their effects on cell proliferation and cisplatin resistance. We also performed EMT, cell migration, and invasion assays in DDP-resistant NSCLC cells overexpressing miR-495 and under-expressing UBE2C. Furthermore, in silico assays coupled with western blotting and luciferase assays revealed that UBE2C directly binds to the 5′-UTR of the drug-resistance genes ABCG2 and ERCC1. Furthermore, miR-495 downregulated ABCG2 and ERCC1 via regulation of UBE2C. Together, the present results indicate that the miR495-UBE2C-ABCG2/ERCC1 axis reverses DDP resistance via downregulation of anti-drug genes and reducing EMT in DDP-resistant NSCLC cells. Keywords: MicroRNA-495, UBE2C, ABCG2, ERCC1, EMT, Cisplatin resistan

Cigarette smoke induces C/EBP-β-mediated activation of miR-31 in normal human respiratory epithelia and lung cancer cells.

BACKGROUND: Limited information is available regarding mechanisms by which miRNAs contribute to pulmonary carcinogenesis. The present study was undertaken to examine expression and function of miRNAs induced by cigarette smoke condensate (CSC) in normal human respiratory epithelia and lung cancer cells. METHODOLOGY: Micro-array and quantitative RT-PCR (qRT-PCR) techniques were used to assess miRNA and host gene expression in cultured cells, and surgical specimens. Software-guided analysis, RNA cross-link immunoprecipitation (CLIP), 3' UTR luciferase reporter assays, qRT-PCR, focused super-arrays and western blot techniques were used to identify and confirm targets of miR-31. Chromatin immunoprecipitation (ChIP) techniques were used to evaluate histone marks and transcription factors within the LOC554202 promoter. Cell count and xenograft experiments were used to assess effects of miR-31 on proliferation and tumorigenicity of lung cancer cells. RESULTS: CSC significantly increased miR-31 expression and activated LOC554202 in normal respiratory epithelia and lung cancer cells; miR-31 and LOC554202 expression persisted following discontinuation of CSC exposure. miR-31 and LOC554202 expression levels were significantly elevated in lung cancer specimens relative to adjacent normal lung tissues. CLIP and reporter assays demonstrated direct interaction of miR-31 with Dickkopf-1 (Dkk-1) and DACT-3. Over-expression of miR-31 markedly diminished Dkk-1 and DACT3 expression levels in normal respiratory epithelia and lung cancer cells. Knock-down of miR-31 increased Dkk-1 and DACT3 levels, and abrogated CSC-mediated decreases in Dkk-1 and DACT-3 expression. Furthermore, over-expression of miR-31 diminished SFRP1, SFRP4, and WIF-1, and increased Wnt-5a expression. CSC increased H3K4Me3, H3K9/14Ac and C/EBP-β levels within the LOC554202 promoter. Knock-down of C/EBP-β abrogated CSC-mediated activation of LOC554202. Over-expression of miR-31 significantly enhanced proliferation and tumorigenicity of lung cancer cells; knock-down of miR-31 inhibited growth of these cells. CONCLUSIONS: Cigarette smoke induces expression of miR-31 targeting several antagonists of cancer stem cell signaling in normal respiratory epithelia and lung cancer cells. miR-31 functions as an oncomir during human pulmonary carcinogenesis

Lsh is involved in de novo methylation of DNA

Deletion of Lsh perturbs DNA methylation patterns in mice yet it is unknown whether Lsh plays a direct role in the methylation process. Two types of methylation pathways have been distinguished: maintenance methylation by Dnmt1 occurring at the replication fork, and de novo methylation established by the methyltransferases Dnmt3a and Dnmt3b. Using an episomal vector in Lsh−/− embryonic fibroblasts, we demonstrate that the acquisition of DNA methylation depends on the presence of Lsh. In contrast, maintenance of previously methylated episomes does not require Lsh, implying a functional role for Lsh in the establishment of novel methylation patterns. Lsh affects Dnmt3a as well as Dnmt3b directed methylation suggesting that Lsh can cooperate with both enzymatic activities. Furthermore, we demonstrate that embryonic stem cells with reduced Lsh protein levels show a decreased ability to silence retroviral vector or to methylate endogenous genes. Finally, we demonstrate that Lsh associates with Dnmt3a or Dnmt3b but not with Dnmt1 in embryonic cells. These results suggest that the epigenetic regulator, Lsh, is directly involved in the control of de novo methylation of DNA