New insights into the activation of Radiation Desiccation Response regulon in Deinococcus radiodurans

The highly radiation-resistant bacterium Deinococcus radiodurans responds to gamma radiation or desiccation through the coordinated expression of genes belonging to Radiation and Desiccation Resistance/Response (RDR) regulon. RDR regulon is operated through cis-acting sequence RDRM (Radiation Desiccation Response Motif), trans-acting repressor DdrO and protease IrrE (also called PprI). The present study evaluated whether RDR regulon controls the response of D. radiodurans to various other DNA damaging stressors, to which it is resistant, such as UV rays, mitomycin C (MMC), methyl methanesulfonate (MMS), ethidium bromide (EtBr), etc. Activation of 3 RDR regulon genes (ddrB, gyrB and DR1143) was studied by tagging their promoter sequences with a highly sensitive GFP reporter. Here we demonstrated that all the DNA damaging stressors elicited activation of RDR regulon of D. radiodurans in a dose-dependent and RDRM-/IrrE-dependent manner. However, ROS-mediated indirect effects [induced by hydrogen peroxide (H₂O₂), methyl viologen (MV), heavy metal/metalloid (zinc or tellurite), etc.] did not activate RDR regulon. We also showed that level of activation was inversely proportional to cellular abundance of repressor DdrO. Our data strongly suggests that direct DNA damage activates RDR regulon in D. radiodurans.

Stochastic transcription in the p53-mediated response to DNA damage is modulated by burst frequency

Discontinuous transcription has been described for different mammalian cell lines and numerous promoters. However, our knowledge of how the activity of individual promoters is adjusted by dynamic signaling inputs from transcription factors is limited. To address this question, we characterized the activity of selected target genes that are regulated by pulsatile accumulation of the tumor suppressor p53 in response to ionizing radiation. We performed time-resolved measurements of gene expression at the single-cell level by smFISH and used the resulting data to inform a mathematical model of promoter activity. We found that p53 target promoters are regulated by frequency modulation of stochastic bursting and can be grouped along three archetypes of gene expression. The occurrence of these archetypes cannot solely be explained by nuclear p53 abundance or promoter binding of total p53. Instead, we provide evidence that the time-varying acetylation state of p53's C-terminal lysine residues is critical for gene-specific regulation of stochastic bursting.

Optogenetic control of Bacillus subtilis gene expression

The Gram-positive bacterium Bacillus subtilis exhibits complex spatial and temporal gene expression signals. Although optogenetic tools are ideal for studying such processes, none has been engineered for this organism. Here, we port a cyanobacterial light sensor pathway comprising the green/red photoreversible two-component system CcaSR, two metabolic enzymes for production of the chromophore phycocyanobilin (PCB), and an output promoter to control transcription of a gene of interest into B. subtilis. Following an initial non-functional design, we optimize expression of pathway genes, enhance PCB production via a translational fusion of the biosynthetic enzymes, engineer a strong chimeric output promoter, and increase dynamic range with a miniaturized photosensor kinase. Our final design exhibits over 70-fold activation and rapid response dynamics, making it well-suited to studying a wide range of gene regulatory processes. In addition, the synthetic biology methods we develop to port this pathway should make B. subtilis easier to engineer in the future.

Gene hypermethylation in blood leukocytes in humans long term after radiation exposure - Validation set

Hypermethylation of СpG islands in the promoter regions of several genes with basic protective function in blood leukocytes of individuals exposed to ionizing radiation long time ago (2-46 years), and differential effects of age and radiation exposure on hypermethylation was reported in our previous work. To validate these results, epigenetic modifications were assessed in an independent series of 49 nuclear industry workers from the "Mayak" facility (67-84 years old at sampling) with documented individual accumulated doses from the prolonged external γ-radiation exposure (95.9-409.5 cGy, end of work with radiation:0.3-39 years ago), and in 50 non-exposed persons matched by age. In addition to the genes analyzed before (RASSF1A, p16/INK4A, p14/ARF, GSTP1), four additional loci were analyzed: TP53, ATM, SOD3, ESR1. The frequency of individuals displaying promoter methylation of at least one of the 8 genes (71.4%) was significantly higher in exposed group as compared to the control group (40%), p = .002, OR = 3.75. A significantly elevated frequency of individuals with hypermethylated СpG islands in GSTP1, TP53, SOD3 promoters was revealed among exposed subjects as compared to the control group (p = .012, OR = 8.41; p = .041, OR = 4.02 and p = .009, OR = 3.42, respectively). A similar trend (p = .12, OR = 3.06) was observed for the p16/INK4A gene. As a whole, p16/INK4A and GSTP1 promoter hypermethylation in irradiated subjects from both previously and currently analyzed groups was pronounced. Thus, the direction of the effects was fully confirmed, suggesting the result reproducibility. No statistically significant correlation between promoter methylation and individual radiation dose was found. Further studies are required to create an array of blood epigenetic markers of radiation exposure associating with premature aging and age-related diseases and to accurately evaluate radiation-added effect across the range of doses.

SYNTHESIS

The results of studies of epigenetic changes in two independent samples of irradiated subjects indicated the significance of radiation factor in the induction of hypermethylation of CpG islands in gene promoters that is revealed in blood cells years and decades after exposure.

Patients Affected by Unmethylated O(6)-Methylguanine-DNA Methyltransferase Glioblastoma Undergoing Radiochemotherapy May Benefit from Moderately Dose-Escalated Radiotherapy

PURPOSE

To compare the therapeutic results of two radiotherapy (RT) dose schedules in combined temozolomide- (TMZ-) RT treatment in newly diagnosed glioblastoma (GB), according to the O(6)-methylguanine-DNA methyltransferase (MGMT) methylation status.

MATERIAL AND METHOD

Patients received either standard (60 Gy) or moderately escalated dose (70 Gy) radiotherapy (RT) with concomitant and adjuvant TMZ between June 2006 and October 2013. We retrospectively evaluated the therapeutic effectiveness of RT schedules in terms of Overall Survival (OS) and Progression-Disease Free Survival (PDFS) analyzing the MGMT methylation status.

RESULTS

One hundred and seventeen patients were selected for the present analysis. Seventy-two out of the selected cases received the standard RT-TMZ course (SDRT-TMZ) whereas the remaining 45 underwent the escalated schedule (HDRT-TMZ). The analysis according to the MGMT promoter methylation status showed that, in unmethylated-MGMT GB patients, HDRT-TMZ and SDRT-TMZ groups had different median OS (p = 0,01) and PDFS (p = 0,007), that is, 8 months and 5 months for the SDRT-TMZ group and 14 months and 9 months for the HDRT-TMZ group, respectively. No difference in survival outcomes was found in methylated MGMT patients according to the two RT schedules (p = 0,12).

CONCLUSIONS

In our experience, unmethylated-MGMT GB patients benefited from a moderately escalated dose of RT plus TMZ.

Heme oxygenase up-regulation under ultraviolet-B radiation is not epigenetically restricted and involves specific stress-related transcriptions factors

Heme oxygenase-1 (HO-1) plays a protective role against oxidative stress in plants. The mechanisms regulating its expression, however, remain unclear. Here we studied the methylation state of a GC rich HO-1 promoter region and the expression of several stress-related transcription factors (TFs) in soybean plants subjected to ultraviolet-B (UV-B) radiation. Genomic DNA and total RNA were isolated from leaves of plants irradiated with 7.5 and 15kJm-2 UV-B. A 304bp HO-1 promoter region was amplified by PCR from sodium bisulfite-treated DNA, cloned into pGEMT plasmid vector and evaluated by DNA sequencing. Bisulfite sequencing analysis showed similar HO-1 promoter methylation levels in control and UV-B-treated plants (C: 3.4±1.3%; 7.5: 2.6±0.5%; 15: 3.1±1.1%). Interestingly, HO-1 promoter was strongly unmethylated in control plants. Quantitative RT-PCR analysis of TFs showed that GmMYB177, GmMYBJ6, GmWRKY21, GmNAC11, GmNAC20 and GmGT2A but not GmWRK13 and GmDREB were induced by UV-B radiation. The expression of several TFs was also enhanced by hemin, a potent and specific HO inducer, inferring that they may mediate HO-1 up-regulation. These results suggest that soybean HO-1 gene expression is not epigenetically regulated. Moreover, the low level of HO-1 promoter methylation suggests that this antioxidant enzyme can rapidly respond to environmental stress. Finally, this study has identified some stress-related TFs involved in HO-1 up-regulation under UV-B radiation.

In silico analysis of 3 expansin gene promoters reveals 2 hubs controlling light and cytokinins response during bud outgrowth

Bud outgrowth is under the intricate control of environmental and endogenous factors. In a recent paper, ¹ we demonstrated that light perceived by Rosa buds triggers cytokinins (CK) synthesis within 3 hours in the adjacent node followed by their transport to the bud. There, CK control expression of a set of major genes (strigolactones-, auxin-, sugar sink strength-, cells division and elongation-related genes) leading to bud outgrowth in light. Conversely, under dark condition, CK accumulation and transport to the bud are repressed and no bud outgrowth occurs. In this paper, we show that the 3 expansin genes RhEXPA1,2,3 are under the control of both light and CK during bud outgrowth. In silico analysis of promoter sequences highlights 2 regions enriched in light and CK cis-regulatory elements as well as a specific cis-element in pRhEXPA3, potentially responsible for the expression patterns observed in response to CK and light.

TERT promoter mutations: a genetic signature of benign and malignant thyroid tumours occurring in the context of tinea capitis irradiation

OBJECTIVE

The aim of this study is to evaluate the frequency and molecular characteristics of TERTp mutations in thyroid adenomas and carcinomas occurring in the low-dose radiation exposure tinea capitis setting.

DESIGN AND METHODS

Twenty-seven patients with 34 well-differentiated thyroid carcinomas and 28 patients with 29 follicular adenomas diagnosed in a Portuguese tinea capitis cohort were studied. Blood samples were obtained from all the patients. Screening for TERTp mutations was performed by PCR amplification followed by Sanger sequencing. A series of 33 sporadic thyroid adenomas was used as control.

RESULTS

TERTp mutations were detected in six of the 28 patients with adenoma (21.4%) and in four of the 27 patients with carcinoma (14.8%). Three tumours (two carcinomas and one adenoma) had the tandem mutation -124/-125 GG>AA (30.0%), whereas the remaining seven had the -124G > A. The 20.7% frequency of TERTp mutations in adenomas contrasts with the absence of mutations in the adenomas from the control group and from most series on record, whereas the one found in carcinomas (11.8%) is similar to those reported in the literature for sporadic carcinomas.

CONCLUSION

TERTp mutations, including the tandem mutation -124/-125 GG>AA not described previously in thyroid tumours, appear to represent a genetic signature for thyroid tumours in patients submitted to low-dose X-ray irradiation. The high frequency of TERTp mutations in the adenomas of our cohort contrasts with their absence in sporadically occurring, as well as in adenomas of the Chernobyl series.

Light-Responsive Promoters

Recent advances in the development of light-inducible transgene expression systems have overcome many inherent drawbacks of conventional chemically regulated systems. The latest generation of those light-regulated systems that are specifically responsive to different wavelengths allows spatiotemporal control of gene expression in a so far unprecedented manner.In this chapter, we first describe the available light-inducible gene expression systems compatible with mammalian cells and explain their underlying mechanisms. Afterward, we give a detailed protocol for the implementation of a UVB light-inducible expression system in mammalian cells.

Tiron Inhibits UVB-Induced AP-1 Binding Sites Transcriptional Activation on MMP-1 and MMP-3 Promoters by MAPK Signaling Pathway in Human Dermal Fibroblasts

Recent research found that Tiron was an effective antioxidant that could act as the intracellular reactive oxygen species (ROS) scavenger or alleviate the acute toxic metal overload in vivo. In this study, we investigated the inhibitory effect of Tiron on matrix metalloproteinase (MMP)-1 and MMP-3 expression in human dermal fibroblast cells. Western blot and ELISA analysis revealed that Tiron inhibited ultraviolet B (UVB)-induced protein expression of MMP-1 and MMP-3. Real-time quantitative PCR confirmed that Tiron could inhibit UVB-induced mRNA expression of MMP-1 and MMP-3. Furthermore, Tiron significantly blocked UVB-induced activation of the MAPK signaling pathway and activator protein (AP)-1 in the downstream of this transduction pathway in fibroblasts. Through the AP-1 binding site mutation, it was found that Tiron could inhibit AP-1-induced upregulation of MMP-1 and MMP-3 expression through blocking AP-1 binding to the AP-1 binding sites in the MMP-1 and MMP-3 promoter region. In conclusion, Tiron may be a novel antioxidant for preventing and treating skin photoaging UV-induced.

Hypermethylation of gene promoters in peripheral blood leukocytes in humans long term after radiation exposure

Some human genes known to undergo age-related promoter hypermethylation. These epigenetic modifications are similar to those occurring in the course of certain diseases, e.g. some types of cancer, which in turn may also associate with age. Given external genotoxic factors may additionally contribute to hypermethylation, this study was designed to analyzes, using methylation-sensitive polymerase chain reaction (PCR), the CpG island hypermethylation in RASSF1A, CDKN2A (including p16/INK4A and p14/ARF) and GSTP1 promoters in peripheral blood leukocytes of individuals exposed to ionizing radiation long time ago. One hundred and twenty-four irradiated subjects (24-77 years old at sampling: 83 Chernobyl Nuclear Power Plant clean-up workers, 21 nuclear workers, 20 residents of territories with radioactive contamination) and 208 unirradiated volunteers (19-77 years old at sampling) were enrolled. In addition, 74 non-exposed offspring (2-51 years old at sampling) born to irradiated parents were examined. The frequency of individuals displaying promoter methylation of at least one gene in exposed group was significantly higher as compared to the control group (OR=5.44, 95% CI=2.62-11.76, p=3.9×10(-7)). No significant difference was found between the frequency of subjects with the revealed promoter methylation in the group of offspring born to irradiated parents and in the control group. The increase in the number of methylated loci of RASSF1A and p14/ARF was associated with age (β=0.242; p=1.7×10(-5)). In contrast, hypermethylation of p16/INK4A and GSTP1 genes correlated with the fact of radiation exposure only (β=0.290; p=1.7×10(-7)). The latter finding demonstrates that methylation changes in blood leukocytes of healthy subjects exposed to radiation resemble those reported in human malignancies. Additional studies are required to identify the dose-response of epigenetic markers specifically associating with radiation-induced premature aging and/or with the development of age-associated cancer and non-cancer diseases.

OsHAL3, a Blue Light-Responsive Protein, Interacts with the Floral Regulator Hd1 to Activate Flowering in Rice

In flowering plants, photoperiodic flowering is controlled by a complicated network. Light is one of the most important environmental stimuli that control the timing of the transition from vegetative growth to reproductive development. Several photoreceptors, including PHYA, PHYB, CRY2, and FKF1 in Arabidopsis and their homologs (OsPHYA, OsPHYB, OsPHYC, and OsCRY2) in rice, have been identified to be related to flowering. Our previous study suggests that OsHAL3, a flavin mononucleotide-binding protein, may function as a blue-light sensor. Here, we report the identification of OsHAL3 as a positive regulator of flowering in rice. OsHAL3 overexpression lines exhibited an early flowering phenotype, whereas downregulation of OsHAL3 expression by RNA interference delayed flowering under an inductive photoperiod (short-day conditions). The change in flowering time was not accompanied by altered Hd1 expression but rather by reduced accumulation of Hd3a and MADS14 transcripts. OsHAL3 and Hd1 colocalized in the nucleus and physically interacted in vivo under the dark, whereas their interaction was inhibited by white or blue light. Moreover, OsHAL3 directly bound to the promoter of Hd3a, especially before dawn. We conclude that OsHAL3, a novel light-responsive protein, plays an essential role in photoperiodic control of flowering time in rice, which is probably mediated by forming a complex with Hd1. Our findings open up new perspectives on the photoperiodic flowering pathway.

Functional characterization and analysis of the Arabidopsis UGT71C5 promoter region

In the present study, we isolated an Arabidopsis promoter, UGT71C5, and analyzed its role in the regulation of the light response mechanism. We constructed a fusion vector pBI121-pU-GUS by integrating the UGT71C5 promoter upstream of the GUS reporter gene in pBI121, and then transferred this vector into Arabidopsis plants. The GUS activity of the transgenic plants was detected using a spectrophotometer under normal growth conditions as well as under light, drought, and ABA stress-treatments. The obtained results indicated that the GUS activity of transgenic plants ranged in between the activities observed in wild-type and 35S transgenic plants, which were used as positive control. Light stress for 8 and 12 h increased the GUS activity in transgenic plants by 3 and 4 times, respectively, compared to the activity in these plants under normal conditions. No such change in the GUS activity was observed under drought and ABA-treated conditions. This suggests that the UGT71C5 promoter is light inducible. Our study provides helpful insights into the elucidation of inducible promoters in Arabidopsis and the molecular mechanisms of light response.

[Photoreactivating Activity of Bioluminescence: Repair of UV-damaged DNA of Escherichia coli Occurs with Assistance of lux-Genes of Marine Bacteria]

The UV resistance of luminescent bacteria Escherichia coli AB1886 uvrA6 (pLeo1) containing the plasmid with luxCDABE genes of marine bacteria Photobacterium leiognathi is approximately two times higher than the UV resistance of non-luminous bacteria E. coli AB1886 uvrA6. Introduction of phr::kan(r) mutations (a defect in the functional activity of photolyase) into the genome of E. coli AB1886 uvrA6 (pLeo1) completely removes the high UV resistance of the cells. Therefore, photoreactivation that involves bacterial photolyase contributes mainly to the bioluminescence-induced DNA repair. It is shown that photoreactivating activity of bioluminescence of P. leiognathi is about 2.5 times lower compared with that one induced by a light source with λ > 385 nm. It is also shown that an increase in the bioluminescence intensity, induced by UV radiation in E. coli bacterial cells with a plasmid containing the luxCD ABE genes under RecA-LexA-regulated promoters, occurs only 25-30 min later after UV irradiation of cells and does not contribute to DNA repair. A quorum sensing regulatory system is not involved in the DNA repair by photolyase.

Fibulin-3 negatively regulates ALDH1 via c-MET suppression and increases γ-radiation-induced sensitivity in some pancreatic cancer cell lines

Fibulin-3 (FBLN-3) has been postulated to be either a tumor suppressor or promoter depending on the cell type, and hypermethylation of the FBLN-3 promoter is often associated with human disease, especially cancer. We report that the promoter region of the FBLN-3 was significantly methylated (>95%) in some pancreatic cancer cell lines and thus FBLN-3 was poorly expressed in pancreatic cancer cell lines such as AsPC-1 and MiaPaCa-2. FBLN-3 overexpression significantly down-regulated the cellular level of c-MET and inhibited hepatocyte growth factor-induced c-MET activation, which were closely associated with γ-radiation resistance of cancer cells. Moreover, we also showed that c-MET suppression or inactivation decreased the cellular level of ALDH1 isozymes (ALDH1A1 or ALDH1A3), which serve as cancer stem cell markers, and subsequently induced inhibition of cell growth in pancreatic cancer cells. Therefore, forced overexpression of FBLN-3 sensitized cells to cytotoxic agents such as γ-radiation and strongly inhibited the stemness and epithelial to mesenchymal transition (EMT) property of pancreatic cancer cells. On the other hand, if FBLN3 was suppressed in FBLN-3-expressing BxPC3 cells, the results were opposite. This study provides the first demonstration that the FBLN-3/c-MET/ALDH1 axis in pancreatic cancer cells partially modulates stemness and EMT as well as sensitization of cells to the detrimental effects of γ-radiation.

Irradiation-induced hippocampal neurogenesis impairment is associated with epigenetic regulation of bdnf gene transcription

Radiotherapy is often employed for the treatment of head and neck cancer. Unfortunately, its neurotoxic effects on normal brain tissue often compromise the quality of life (QOL) for survivors. Particularly, acute cognitive deficit (ACD), which can occur several days to one month after irradiation, limits its therapeutic use. Impairment of neurogenesis in the hippocampus plays a key role in the development of radiation-induced cognitive deficit, and brain-derived neurotrophic factor (BDNF) may be involved. In the present study, we re-evaluated the effects of different doses of radiation on the development of ACD in Sprague Dawley rats. Our results showed that 30 Gy, but not 2 Gy or 10 Gy of whole brain radiation (WBI), led to significant deficits in cognitive functions at one month post-irradiation. At 7 and 30 days post-irradiation, immunofluorescence showed WBI had seriously impeded the production of new neurons and shortened their survival time. Additionally, decreased bdnf mRNA and protein expression were also observed. A significant decrease in histone deacetylase 1 (HDAC1)-dependent H3 acetylation was observed at bdnf promoters by ChIP analysis. TSA, an HDAC inhibitor, triggered bdnf transcription and rescued neurogenesis impairment following WBI. In summary, our results suggest that a single-dose exposure to 30 Gy WBI induced acute cognitive dysfunction in rats. Additionally, radiation-induced persistent inhibition of bdnf gene transcription resulting from lowered rates of HDAC1-dependent H3 acetylation was associated with long-term impairment of neurogenesis in the denate gyrus (DG). Triggering of BDNF-TrkB signaling by inhibition of HDAC-1 may be used to stimulate neurogenesis.

[The study of aberrant methylation in blood leukocytes of liquidators of the Chernobyl accident]

The study of aberrant methylation of CpG islands in the promoter regions of genes (P16/CDKN2A, P14/ARF, RASSF1A, GSTP1) in blood leukocytes of liquidators of the Chernobyl accident (n = 83, 38-76 years of age) and control subjects of two groups (n = 48, age ≤ 35 and n = 65, age > 35) was carried out using methylation-sensitive restriction endonuclease analysis followed by PCR. The total number of AciI sites in the analyzed fragments ranged from 2 to 7 for different genes. Only 1 subject (2.1%) from the control group (healthy young individuals, age ≤ 35) has methylation of the studied CpG--dinucleotides of RASSF1A gene. Promoter methylation of at least one of the genes analyzed was observed in 28.92% liquidators and significantly exceeded (p = 0.016) such rate in a one-age (> 35 years of age) control group (12.31%). A significantly elevated frequency (p = 0.023) of individuals with abnormal methylation of GSTP1 gene in the group of liquidators as compared to the control group was revealed. The occurrence of promoter methylation of RASSF1A gene significantly correlated with aging both in the control group (r = 0.214; p = 0.023) and in the liquidators of the Chernobyl accident (r = 0.230; p = 0.036). No similar trend was found for other genes. Multiple regression analysis showed that the growth in the number of methylated loci of a set of genes p16, p14 and GSTP1 is exclusively due to the fact of exposure (OR = 7.32, 95% CI = 2.49-25.83, p-value = 2.7 x 10(-5)). The results obtained demonstrate for the first time the reality of the radiation-induced aberrant methylation of CpG islands in promoters of genes involved in the basic protective, functions of cells in the human body in remote periods after radiation exposure.

Expression of the high light-inducible Dunaliella LIP promoter in Chlamydomonas reinhardtii

The development of highly inducible promoters is critical for designing effective transformation systems for transgenic analyses. In this study, we investigated the promoter of the light-inducible protein gene (LIP) of the marine alga Dunaliella sp. LIPs are homologs of the early light-induced proteins (ELIPs) of Arabidopsis thaliana. DNA sequence analysis revealed that the LIP promoter contains several light-responsive motifs. Constructs containing progressive truncations of the LIP promoter fused with a Renilla luciferase gene were introduced into Chlamydomonas reinhardtii to identify the light-responsive region in the promoter. Transcription from the LIP promoter was stimulated by high light (HL) in a light intensity-dependent manner. In contrast, oxidative stress induced by chemicals had little effect on the LIP promoter, which implies that the LIP promoter is exclusively induced by high light. Truncation of the promoter to a -100 base pair (bp) region abrogated light inducibility, which suggests the presence of a negative cis-regulatory element upstream of the -100 bp fragment. The LIP promoter can be utilized in transgenic research to specifically select and propagate transgenic microalgae under high-light conditions.

Light and abiotic stresses regulate the expression of GDP-L-galactose phosphorylase and levels of ascorbic acid in two kiwifruit genotypes via light-responsive and stress-inducible cis-elements in their promoters

Ascorbic acid (AsA) plays an essential role in plants by protecting cells against oxidative damage. GDP-L-galactose phosphorylase (GGP) is the first committed gene for AsA synthesis. Our research examined AsA levels, regulation of GGP gene expression, and how these are related to abiotic stresses in two species of Actinidia (kiwifruit). When leaves were subjected to continuous darkness or light, ABA or MeJA, heat, or a hypoxic environment, we found some correlation between the relative levels of GGP mRNA and AsA concentrations. In transformed tobacco plants, activity of the GGP promoter was induced by all of these treatments. However, the degree of inducibility in the two kiwifruit species differed among the GGP promoter deletions. We deduced that the G-box motif, a light-responsive element, may have an important function in regulating GGP transcripts under various light conditions in both A. deliciosa and A. eriantha. Other elements such as ABRE, the CGTCA motif, and HSE might also control the promoter activities of GGP in kiwifruit. Altogether, these data suggest that GGP expression in the two kiwifruit species is regulated by light or abiotic stress via the relative cis-elements in their promoters. Furthermore, GGP has a critical role in modulating AsA concentrations in kiwifruit species under abiotic stresses.

REDD1 protects osteoblast cells from gamma radiation-induced premature senescence

Radiotherapy is commonly used for cancer treatment. However, it often results in side effects due to radiation damage in normal tissue, such as bone marrow (BM) failure. Adult hematopoietic stem and progenitor cells (HSPC) reside in BM next to the endosteal bone surface, which is lined primarily by hematopoietic niche osteoblastic cells. Osteoblasts are relatively more radiation-resistant than HSPCs, but the mechanisms are not well understood. In the present study, we demonstrated that the stress response gene REDD1 (regulated in development and DNA damage responses 1) was highly expressed in human osteoblast cell line (hFOB) cells after γ irradiation. Knockdown of REDD1 with siRNA resulted in a decrease in hFOB cell numbers, whereas transfection of PCMV6-AC-GFP-REDD1 plasmid DNA into hFOB cells inhibited mammalian target of rapamycin (mTOR) and p21 expression and protected these cells from radiation-induced premature senescence (PS). The PS in irradiated hFOB cells were characterized by significant inhibition of clonogenicity, activation of senescence biomarker SA-β-gal, and the senescence-associated cytokine secretory phenotype (SASP) after 4 or 8 Gy irradiation. Immunoprecipitation assays demonstrated that the stress response proteins p53 and nuclear factor κ B (NFkB) interacted with REDD1 in hFOB cells. Knockdown of NFkB or p53 gene dramatically suppressed REDD1 protein expression in these cells, indicating that REDD1 was regulated by both factors. Our data demonstrated that REDD1 is a protective factor in radiation-induced osteoblast cell premature senescence.

[Anti-tumor effect of suicide gene therapy using chimeric promoter plus radiotherapy on cancer cell lines]

OBJECTIVE

To explore the synergistic anti-tumor effect of radiotherapy and horseradish peroxidase/prodrug indole-3-acetic acid (HRP/IAA) gene therapy system using chimeric hTERT promoter responsive to ionizing radiation.

METHODS

The synthetic hTERT promoters containing four tandem-repeat copies of radio-inducible CArG elements, and the chimeric promoter containing cytomegalovirus (CMV) early promoter were both constructed. The activities of the chimeric promoters in cancer cell lines (HeLa, A549, and MHCC97) and normal cell line (MRC-5) were detected using luciferase reporter gene expression analysis after a (60)Co γ-irradiation treatment at a series of doses(a single dose of 0 to 10 Gy). The anti-tumor effect of combining irradiation with HRP/IAA gene-directed enzyme prodrug therapy system controlled by the chimeric promoter was tested by colony formation assay, cell counting and apoptosis analysis.

RESULTS

The chimeric promoters were ineffective in normal human cells, even after irradiation, but the expression of luciferase gene in tumor cells was significantly higher. The activity of the chimeric promoter in MRC-5 cells was 22.3%, 12.9% and 13.6% of that in HeLa, A549 and MHCC97 cells, respectively. After irradiation, the ratios were 11.7%, 8.7% and 8.8%, respectively. Furthermore, the chimeric promoters could successfully induce the expression of luciferase gene following different doses of radiation, with maximal inducible activity seen after 6 Gy irradiation. The chimeric promoter containing four tandem-repeat copies of radio-inducible CArG elements and CMV early promoter showed the highest activity with 6 Gy irradiation. The relative luciferase activities in HeLa, A549 and MHCC97 cells were 1.7 ± 0.2, 2.3 ± 0.2 and 2.3 ± 0.1, respectively. The chimeric promoter mediated suicide gene therapy system could increase radio-sensitivity in different cancer cells. Compared with the control system, it plus irradiation showed stronger cell proliferation inhibition, 67.3% vs. 26.1% in HeLa, 69.0% vs. 28.3% in A549, 64.6% vs. 20.8% in MHCC97 cells, and also higher apoptosis-inducing effect, 39.6% vs. 14.2% in HeLa, 33.0% vs. 12.4% in A549, and 33.2% vs. 14.2% in MHCC97 cells.

CONCLUSIONS

Chimeric promoter containing hTERT promoter, CArG elements and CMV promoter preserve the tumor-specificity in telomerase-positive tumor cells, and irradiation-responsive to low dose of radiation. The suicide gene therapy using this promoter plus radiotherapy show a strong anti-tumor effect in vitro. It is expected to have a good potential for future application in gene radiotherapy.

Thyrotroph embryonic factor regulates light-induced transcription of repair genes in zebrafish embryonic cells

Numerous responses are triggered by light in the cell. How the light signal is detected and transduced into a cellular response is still an enigma. Each zebrafish cell has the capacity to directly detect light, making this organism particularly suitable for the study of light dependent transcription. To gain insight into the light signalling mechanism we identified genes that are activated by light exposure at an early embryonic stage, when specialised light sensing organs have not yet formed. We screened over 14,900 genes using micro-array GeneChips, and identified 19 light-induced genes that function primarily in light signalling, stress response, and DNA repair. Here we reveal that PAR Response Elements are present in all promoters of the light-induced genes, and demonstrate a pivotal role for the PAR bZip transcription factor Thyrotroph embryonic factor (Tef) in regulating the majority of light-induced genes. We show that tefβ transcription is directly regulated by light while transcription of tefα is under circadian clock control at later stages of development. These data leads us to propose their involvement in light-induced UV tolerance in the zebrafish embryo.

Surgical resection after TNFerade therapy for locally advanced pancreatic cancer

CONTEXT

Treatment of pancreatic cancer remains a major oncological challenge and survival is dismal. Most patients, present with advanced disease at diagnosis and are not candidates for curative resection. Preoperative chemoradiation may downstage and improve survival in locally advanced pancreatic cancer. This has prompted investigators to look for novel neoadjuvant therapies. Gene therapy for pancreatic cancer is a novel investigational approach that may have promise. TNFerade is a replication deficient adenovirus vector carrying the human tumor necrosis factor (TNF)-alpha gene regulated under control of a radiation-inducible gene promoter. Transfection of tumor cells with TNFerade maximizes the antitumor effect of TNF-alpha under influence of radiation leading to synergistic effects in preclinical studies.

CASE REPORT

We describe a case of locally advanced unresectable pancreatic cancer treated with a novel multimodal approach utilizing gene therapy with TNFerade and concurrent chemoradiation that was followed by successful surgical resection.

CONCLUSION

Neoadjuvant TNFerade based chemoradiation therapy may be a useful adjunct to treatment of locally advanced pancreatic cancer.

Radiation to control transgene expression in tumors

Significant evidence has accumulated indicating that certain genes are induced by ionising radiation. An implication of this observation is that their promoter regions include radiation-responsive sequences. These sequences have been isolated in the promoter of several genes including Erg-1, p21/WAF-1, GADD45alpha and t-PA. The mechanism by which radiation induces gene expression remains unclear but involves putative binding sites for selected transcription factors and/or p53. Consensus CC(A/T)6GG sequences have been localized in the Erg-1 promoter and are referred to as serum response elements or CArG elements. The tandem combination of CArG elements has been shown to improve gene expression levels, with a 9-copy motif conferring maximum inducibility. The response of these genes to ionising radiation appears to follow a sigmoid relationship with time and dose. Therapeutic induction of suicide genes and significant cytotoxicity can be achieved at clinically relevant x-rays doses both in vitro and in vivo but was found to be cell-type dependent. Radiation-inducible gene therapy can be potentially enhanced by exploiting hypoxia through the inclusion of hypoxia-response element motifs in the expression cassette, the use of the anaerobic bacteria or the use of neutron irradiation. These results are encouraging and provide significant evidence that gene therapy targeted to the radiation field is a reasonably attractive therapeutic option and could help overcome hypoxic radioresistant tumors.

Interaction of the Arabidopsis UV-B-specific signaling component UVR8 with chromatin

Arabidopsis UV RESISTANCE LOCUS8 (UVR8) is a UV-B-specific signaling component that regulates expression of a range of genes concerned with UV protection. Here, we investigate the interaction of UVR8 with chromatin. Using antibodies specific to UVR8 in chromatin immunoprecipitation (ChIP) assays with wild-type plants, we show that native UVR8 binds to chromatin in vivo. Similar experiments using an anti-GFP antibody with plants expressing a GFP-UVR8 fusion show that UVR8 associates with a relatively small region of chromatin containing the HY5 gene. UVR8 interacts with chromatin containing the promoter regions of other genes, but not with all the genes it regulates. UV-B is not required for the interaction of UVR8 with chromatin because association with several gene loci is observed in the absence of UV-B. Pull-down assays demonstrate that UVR8 associates with histones in vivo and competition experiments indicate that the interaction is preferentially with histone H2B. ChIP experiments using antibodies that recognize specific histone modifications indicate that the UV-B-stimulated transcription of some genes may be correlated with histone modification. In particular, the ELIP1 promoter showed a significant enrichment of diacetyl histone H3 (K9/K14) following UV-B exposure. These findings increase understanding of the interaction of the key UV-B-specific regulator UVR8 with chromatin.