No enhancing effects of plasmid-specific histone acetyltransferase recruitment system on transgene expression in vivo

Abstract

Altered levels of histone acetylation are associated with changes in chromosomal gene expression. Thus, the specific acetylation of histones bound to plasmid DNA might increase transgene expression. Previously, the expression of the histone acetyltransferase domain of CREB-binding protein fused to the sequence-dependent DNA binding domain of GAL4 (GAL4-HAT) successfully improved reporter gene expression in cultured cells [J. Biosci. Bioengng. 123, 277–280 (2017)]. In this study, the same approach was applied for transgene expression in mice. The activator and reporter plasmid DNAs bearing the genes for GAL4-HAT and Gaussia princeps luciferase, respectively, were co-administered into the mouse liver by hydrodynamics-based tail vein injection, and the Gaussia luciferase activity in serum was measured for two weeks. Unexpectedly, the co-injection of the GAL4-HAT and luciferase plasmid DNAs seemed to decrease, rather than increase, luciferase expression. Moreover, the co-injection apparently reduced the amount of luciferase DNA in the liver. These results indicated that this system is ineffective in vivo and suggested the exclusion of hepatic cells expressing GAL4-HAT.     

膜去极化与cAMP在胰岛细胞株HIT中诱导CBP片段的转录活性

为了研究 Ｃ Ｂ Ｐ在胰岛 Ｈ Ｉ Ｔ 细胞中调节基因转录的机制,将不同的 Ｃ Ｂ Ｐ片段瞬时转染到细胞中,观察其转录活性．实验表明,在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ 均可诱导 Ｃ Ｂ Ｐ３０（ Ｃ Ｒ Ｅ Ｂ结合功能区）转录活性增强,并有协同效应． Ｐ Ｋ Ｃ对 Ｃ Ｂ Ｐ３０ 的转录活性无影响;与 Ｃ Ｒ Ｅ Ｂ有更强结合力的 Ｃ Ｂ Ｐ Ｋ Ｉ Ｘ Ｓ／ Ｂ（氨基酸序列短于 Ｃ Ｂ Ｐ３０ 的 Ｃ Ｒ Ｅ Ｂ结合功能区）其基本转录活性及膜去极化、ｃ Ａ Ｍ Ｐ诱导下的转录活性均比 Ｃ Ｂ Ｐ３０ 更强．反义 Ｃ Ｒ Ｅ Ｂ 的过度表达可降低 ｃ Ａ Ｍ Ｐ诱导的 Ｃ Ｂ Ｐ的转录活性．提示在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ对共转录因子 Ｃ Ｂ Ｐ转录活性的调节作用通过 Ｃ Ｒ Ｅ Ｂ介导．     

Stable luciferase reporter cell lines for signal transduction pathway readout using GAL4 fusion transactivators

While GAL4 fusion activators have been widely used for dissecting signal transduction pathways in transient assays, there has been surprisingly little reported on utilizing cell lines with stably integrated fusion activators. To avoid problems with the efficiency and reproducibility inherent to transient transfection, we describe here the generation and characterization of HeLa reporter cell lines, which contain a stably integrated luciferase gene responsive to stably integrated and constitutively expressed GAL4-CREB or GAL4-Elk1 fusion activators. These cell lines exhibited extremely low basal luciferase expression but robust response to various extracellular stimuli or the expression of signaling molecules that resulted in elevated MAP kinase or PKA activities. This integrated two-component reporter system allows one to focus specifically on particular signaling pathway endpoints and the altered transactivation activity of either Elk1 or CREB. With the procedures described here, many novel cell-based assays can be developed by generating new reporter cell lines with medically important but difficult-to-transfect cell types, and by using different reporter genes or different fusion transactivator genes.     

miR-424-5p regulates apoptosis and cell proliferation via targeting Bcl2 in nucleus pulposus cells

ABSTRACT

miRNAs play an important role in the pathogenesis of intervertebral disc degeneration (IDD). The role and the underlying mechanism of miR-424-5p in human nucleus pulposus (NP) are still unknown. We aimed to explore the role of miR-424-5p in IDD.

Real-time PCR was used to detect the expression of miR-424-5p and Bcl2 in IDD tissues and idiopathic scoliosis tissues. Human NP cells were used in our study. MTT and Hoechst apoptosis assays were used to detect the proliferation and apoptosis of NP cells, respectively. Western blotting assays were used to detect the expression levels of Bcl-2, cleaved caspase-3, cleaved caspase-9, caspase-3 and caspase-9 in degenerative NP cells. A luciferase reporter assay was applied to confirm the relationship between miR-424-5p and Bcl2.

Our results showed that the expression of miR-424-5p was increased and Bcl2 was decreased in degenerative NP cells. miR-425-5p expression was negatively correlated with Bcl2 expression in IDD tissues. Suppression of miR-424-5p using an inhibitor increased Bcl2 expression at both the mRNA and protein levels, and it promoted cell viability and inhibited apoptosis. Furthermore, the levels of cleaved caspase-3 and cleaved caspase-9 were downregulated in miR-424-5p-silenced NP cells. Interestingly, we found that silencing miR-424-5p increased p62 expression at both the mRNA and protein levels. Finally, a luciferase reporter assay verified the binding of the miR-424-5p and the 3’UTR of Bcl2.

These results suggested that silencing miR-424-5p suppressed NP cell apoptosis by upregulating Bcl2. Therefore, miR-424-5p might be a novel target for IDD therapies.     

Myocyte enhancer factor-2 and cardiac muscle gene expression during hibernation in thirteen-lined ground squirrels

Long non-coding RNA urothelial carcinoma associated 1 (UCA1) promotes human bladder cancer cell proliferation, but the underlying mechanism remains unknown. After knocking down of UCA1 in BLZ-211 cells, several cell cycle-related genes (CDKN2B, EP300 and TGFβ-2) were screened by microarray assay and validated by real-time PCR. Interestingly, in western blot analysis, p300 (encoded by EP300) and its coactivator cAMP response element-binding protein (CREB) level were significantly down-regulated. Both suppression of UCA1 expression by shRNA in BLZ-211 cells and ectopic expression of UCA1 in UMUC-2 cells showed that UCA1 alteration paralleled to the expression and phosphorylation of CREB, and UCA1 obviously influenced AKT expression and activity. Furthermore, in BLZ-211 cells, cell cycle progression was greatly reduced after PI3-K pathway was blocked by LY294002, indicating that UCA1 affected cell cycle progression through CREB. Taken together, we concluded that UCA1 regulated cell cycle through CREB via PI3K-AKT dependent pathway in bladder cancer.     

Effect of IL-1beta on CRE-dependent gene expression in human airway smooth muscle cells

IL-1beta inhibits isoproterenol (ISO)-induced relaxation of cultured human airway smooth muscle (HASM) cells. The purpose of this study was to determine whether IL-1beta can also suppress ISO-induced cAMP response element (CRE)-dependent gene expression. ISO (10 microM) caused a marked increase in CRE-binding protein (CREB) phosphorylation, which was attenuated by IL-1beta (2 ng/ml). This effect of IL-1beta was abolished by the cyclooxygenase (COX) inhibitor indomethacin. To examine CRE-driven gene expression, we transiently transfected HASM cells with a construct containing CRE upstream of a luciferase reporter gene. ISO (6 h) caused a sixfold increase in luciferase activity. IL-1beta (24 h) alone also increased luciferase activity, although to a lesser extent (2-fold). However, the ability of ISO to elicit luciferase expression was markedly reduced in cells treated with IL-1beta. Indomethacin, the MEK and p38 inhibitors U-0126 and SB-203580, the protein kinase A inhibitor H-89, and dexamethasone each completely abolished the ability of IL-1beta to induce CRE-driven gene expression but only slightly increased the ability of ISO to induce CRE-driven gene expression in IL-1beta-treated cells. IL-1beta also attenuated dibutyryl cAMP-induced CRE-driven gene expression, but not dibutyryl cAMP-induced CREB phosphorylation. Tumor necrosis factor-alpha (10 ng/ml) also attenuated ISO-induced CRE-driven gene expression, even though it was without effect on ISO-induced cAMP formation or ISO-induced CREB phosphorylation. The results suggest that IL-1beta and tumor necrosis factor-alpha may attenuate the ability of beta-agonists to induce expression of genes with CRE in their regulatory regions at least in part through events downstream of CREB phosphorylation.     

Induction of apoptosis in murine neuroblastoma by systemic delivery of transferrin-shielded siRNA polyplexes for downregulation of Ran

The polymer, OEI-HD, based on beta-propionamide-cross-linked oligoethylenimine and its chemical transferrin conjugate were evaluated for siRNA delivery into murine Neuro2A neuroblastoma cells in vitro and in vivo. An 80% silencing of luciferase expression in neuroblastoma cells, stably transfected with a luciferase gene, was obtained using standard OEI-HD polyplexes or transferrin-conjugated shielded OEI-HD polyplexes. The Ras-related nuclear protein Ran was selected as a therapeutically relevant target protein. Systemic delivery of transferrin-conjugated OEI-HD/RAN siRNA formulations (three intravenous applications at 3 days interval) resulted in >80% reduced Ran protein expression, apoptosis, and a reduced tumor growth in Neuro2A tumors of treated mice. The treatment was not associated with signs of acute toxicity or significant changes in weight, hematology parameters, or liver enzymes (AST, ALT, or AP) of mice. All our results demonstrate that OEI-HD/siRNA formulations can knockdown genes in tumor cells in vitro and in vivo in mice in the absence of unspecific toxicity.     

Lysophosphatidic acid induces neurite retraction in differentiated neuroblastoma cells via GSK-3�� activation

Lysophosphatidic acid (LPA) is a lipid growth factor that exerts diverse biological effects, including rapid neurite retraction and cell migration. Alterations in cell morphology, including neurite retraction, in neurodegenerative disorders such as Alzheimer's disease involve hyperphosphorylation of the cytoskeletal protein tau. Since LPA has been shown to induce neurite retraction in various cultured neural cells and the detailed underlying molecular mechanisms have not yet been elucidated, we investigated whether LPA induced neurite retraction through taumediated signaling pathways in differentiated neuroblastoma cells. When Neuro2a cells differentiated with retinoic acid (RA) were exposed to LPA, cells exhibited neurite retraction in a time-dependent manner. The retraction of neurites was accompanied by the phosphorylation of tau. The LPA-induced neurite retraction and tau phosphorylation in differentiated Neuro2a cells were significantly abolished by the glycogen synthase kinase-3β (GSK-3β) inhibitor lithium chloride. Interestingly, the LPA-stimulated tau phosphorylation and neurite retraction were markedly prevented by the administration of H89, an inhibitor of both cyclic-AMP dependent protein kinase (PKA) and cyclic-AMP response element-binding protein (CREB). Transfection of the dominant-negative CREBs, K-CREB and A-CREB, failed to prevent LPA-induced tau phosphorylation and neurite retraction in differentiated Neuro2a cells. Taken together, these results suggest that GSK-3β and PKA, rather than CREB, play important roles in tau phosphorylation and neurite retraction in LPA-stimulated differentiated Neuro2a cells.