Role of promoter DNA sequence variations on the binding of EGR1 transcription factor

LncRNA HOTAIR regulates the expression of MRP1 gene through the mir-6807-5p/Egr1 axis to affect the multidrug resistance of lung cancer cells

Multi-drug resistance-associated protein 1 (MRP1) plays critical roles in the multi-drug resistance (MDR) of cancer cells, LncRNA HOTAIR is closely related to MDR in lung cancer, however, the effects of HOTAIR on MRP1 expression and MDR in lung cancer cells (A549/DDP) remain unknown. In this study, the effects of HOTAIR on MRP1 gene expression and MDR in A549/DDP cells were monitored. LncRNA HOTAIR was upregulated in A549/DDP cells, and overexpression of HOTAIR promoted MRP1 expression and MDR development. The opposite trend was observed when HOTAIR was silenced in A549/DDP cells. To uncover the role of LncRNA HOTAIR in the MDR of human lung cancer, the effects of Egr1 on MRP1 gene expression and MDR in A549/DDP cells were monitored. The results showed that Egr1 could bind to the MRP1 promoter at site -53/-42 bp and regulate MRP1 expression. Egr1 knock-down reduced MRP1 expression, while Egr1 overexpression increased it. Further, the results demonstrated that LncRNA HOTAIR mediated the effects of Egr1 on MRP1 and MDR via sponging of miR-6807-3p. Moreover, miR-6807-3p exerts its function by targeting the Egr1 3'UTR. In conclusion, the results revealed the novel HOTAIR/miR-6807-3p/Egr1 axis in the regulation of MRP1 expression and MDR in lung cancer cells.

BaP/BPDE suppresses human trophoblast cell migration/invasion and induces unexplained miscarriage by up-regulating a novel lnc-HZ11 in extracellular vesicles: An intercellular study

Extracellular vesicles (EVs) mediate the intercellular crosstalk by transferring functional cargoes. Recently, we have discovered that BaP/BPDE exposure suppresses trophoblast cell migration/invasion and induces miscarriage, which are also regulate by lncRNAs at intracelluar levels. However, the EVs-mediated intercellular regulatory mechanisms are completely unexplored. Specifically, whether EVs might transfer BPDE-induced toxic lncRNA to fresh recipient trophoblast cells and suppress their migration/invasion to further induce miscarriage is completely unknown. In this study, we find that BPDE exposure up-regulates a novel lnc-HZ11, which suppresses EGR1/NF-κB/CXCL12 pathway and migration/invasion of trophoblast cells. Intercellular studies show that EV-HZ11 (lnc-HZ11 in EVs), which is highly expressed in BPDE-exposed donor cells, suppresses EGR1/NF-κB/CXCL12 pathway and migration/invasion in recipient cells by transferring lnc-HZ11 through EVs. Analysis of villous tissues collected from UM (unexplained miscarriage) patients and HC (healthy control) group shows that the levels of BPDE-DNA adducts, lnc-HZ11 or EV-lnc-HZ11, and EGR1/NF-κB/CXCL12 pathway are all associated with miscarriage. Mouse assays show that BaP exposure up-regulates the levels of lnc-Hz11 or EV-Hz11, suppresses Egr1/Nf-κb/Cxcl12 pathway, and eventually induces miscarriage. Knockdown of lnc-Hz11 by injecting EV-AS-Hz11 could effectively alleviate miscarriage in BaP-exposed mice. Furthermore, EV-HZ11 in serum samples could well predict the risk of miscarriage. Collectively, this study not only discovers EVs-HZ11-mediated intercellular mechanisms that BaP/BPDE suppresses trophoblast cell migration/invasion and induces miscarriage but also provides new approach for treatment against unexplained miscarriage through EV-HZ11.

Thermodynamic Additivity for Impacts of Base-Pair Substitutions on Association of the Egr-1 Zinc-Finger Protein with DNA

The transcription factor Egr-1 specifically binds as a monomer to its 9 bp target DNA sequence, GCGTGGGCG, via three zinc fingers and plays important roles in the brain and cardiovascular systems. Using fluorescence-based competitive binding assays, we systematically analyzed the impacts of all possible single-nucleotide substitutions in the target DNA sequence and determined the change in binding free energy for each. Then, we measured the changes in binding free energy for sequences with multiple substitutions and compared them with the sum of the changes in binding free energy for each constituent single substitution. For the DNA variants with two or three nucleotide substitutions in the target sequence, we found excellent agreement between the measured and predicted changes in binding free energy. Interestingly, however, we found that this thermodynamic additivity broke down with a larger number of substitutions. For DNA sequences with four or more substitutions, the measured changes in binding free energy were significantly larger than predicted. On the basis of these results, we analyzed the occurrences of high-affinity sequences in the genome and found that the genome contains millions of such sequences that might functionally sequester Egr-1.