Alteration of gene transcription by inhibition of specific transcriptional regulatory proteins has important therapeutic potential. Synthetic double-stranded phosphorothioate oligonucleotides with high affinity for a target transcription factor can be introduced into cells as decoy cis-elements to bind the factors and alter gene expression. The CRE (cyclic AMP response element)-transcription factor complex is a pleiotropic activator that participates in the induction of a wide variety of cellular and viral genes. Because the CRE cis-element, TGACGTCA, is palindromic, a synthetic single-stranded oligonucleotide composed of the CRE sequence self-hybridizes to form a duplex/hairpin. Herein we report that the CRE-palindromic oligonucleotide can penetrate into cells, compete with CRE enhancers for binding transcription factors, and specifically interfere with CREand AP-1-directed transcription in vivo. These oligonucleotides restrained tumor cell proliferation, without affecting the growth of noncancerous cells. This decoy oligonucleotide approach offers great promise as a tool for defining cellular regulatory processes and treating cancer and other diseases.Eukaryotic transcription is regulated by the interplay of various protein factors at promoters (1, 2). It has been shown that prokaryotic repressors can function as negative regulators of eukaryotic promoters (3,4). This observation suggests that displacement of activating proteins might provide a general strategy for gene-specific repression in eukaryotes. Several approaches have been undertaken to control eukaryotic gene expression through such displacement.In one approach, trans-dominant mutants are generated that interfere with the function of transactivators. Mutants are generated that retain the ability to bind to cis-regulatory DNA sequences but that have dysfunctional transcriptional activation domains. These mutant transcription factors compete with their functional, wild-type counterparts for binding to the enhancer sequences and prevent the activation or repression of the target gene. Although this strategy has been successful, in vitro (5-8), the generation of such mutants is not always possible. The transcription factor must be well characterized such that the activation domain(s) is identified and can be mutated. Also, even with sufficient knowledge to generate such mutants, difficult gene therapy procedures would be required to express these proteins in vivo.Promoter competition strategy has also been utilized whereby plasmids containing cis-acting elements in common with the targeted gene are introduced in high copy number into cells (9). At high copy number, a majority of the transcription factors can be competitively bound away from the native enhancer sequences with gene expression accordingly regulated. Because these plasmids must be stably maintained at high copy number in target cells, a requirement that is difficult to achieve in vivo, this approach has also been limiting.Another alternative is to employ oligonucleotides to form triple heli...

Overexpression of cAMP-dependent protein kinase (PKA) type I isozyme is associated with cell proliferation and neoplastic transformation. The presence of PKA on the external surface of LS-174T human colon carcinoma cells has been shown. Here, we show that cancer cells of various cell types excrete PKA into the conditioned medium. This extracellular PKA (ECPKA) is present in active, free catalytic subunit (C subunit) form, and its activity is specifically inhibited by PKA inhibitory protein, PKI. Overexpression of the C␣ or RI␣ subunit gene of PKA in an expression vector, which upregulates intracellular PKA type I, markedly up-regulates ECPKA expression. In contrast, overexpression of the RII␤ subunit, which eliminates PKA type I, up-regulates PKA type II, and reverts the transformed phenotype, down-regulates ECPKA. A mutation in the C␣ gene that prevents myristylation allows the intracellular PKA up-regulation but blocks the ECPKA increase, suggesting that the NH 2-terminal myristyl group of C␣ is required for the ECPKA expression. In serum of cancer patients, the ECPKA expression is up-regulated 10-fold as compared with normal serum. These results indicate that the ECPKA expression is an ordered cellular response of a living cell to actively exclude excess intracellular PKA molecules from the cell. This phenomenon is up-regulated in tumor cells and has an inverse relationship with the hormone dependency of breast cancer. Thus, the extracellular PKA may serve as a potential diagnostic and prognostic marker for cancer.

UV irradiation has been reported to induce p21WAF1/CIP1 protein degradation through a ubiquitinproteasome pathway, but the underlying biochemical mechanism remains to be elucidated. Here, we show that ser-114 phosphorylation of p21 protein by glycogen synthase kinase 3␤ (GSK-3␤) is required for its degradation in response to UV irradiation and that GSK-3␤ activation is a downstream event in the ATR signaling pathway triggered by UV. UV transiently increased GSK-3␤ activity, and this increase could be blocked by caffeine or by ATR small interfering RNA, indicating ATR-dependent activation of GSK-3␤. ser-114, located within the putative GSK-3␤ target sequence, was phosphorylated by GSK-3␤ upon UV exposure. The nonphosphorylatable S114A mutant of p21 was protected from UV-induced destabilization. Degradation of p21 protein by UV irradiation was independent of p53 status and prevented by proteasome inhibitors. In contrast to the previous report, the proteasomal degradation of p21 appeared to be ubiquitination independent. These data show that GSK-3␤ is activated by UV irradiation through the ATR signaling pathway and phosphorylates p21 at ser-114 for its degradation by the proteasome. To our knowledge, this is the first demonstration of GSK-3␤ as the missing link between UV-induced ATR activation and p21 degradation.

Lung cancer is one of the deadliest and commonly diagnosed neoplasms. Early diagnosis of this disease is critical for improving clinical outcome and prognosis. Because the early stages of lung cancer often produce no symptoms, it is necessary to identify biomarkers for early detection, prognostic evaluation, and recurrence monitoring of the cancer. To identify potential lung cancer biomarkers, we analyzed the differential protein secretion from transformed bronchial epithelial cells (1198 and 1170-I) as compared to immortalized normal bronchial epithelial cells (BEAS-2B) and non-transformed cells (1799) all of which are derived from BEAS-2B and represent multistage bronchial epithelial carcinogenesis. The proteins recovered from the conditioned media of the cells were separated on two-dimensional gels. There was little difference between the secretome of the BEAS-2B and 1799 cells, whereas the patterns between the transformed 1198 and 1170-I cells and non-transformed 1799 cells were significantly different. Using mass spectrometry and database search, we identified 20 proteins including protein gene product 9.5 (PGP9.5), translationally controlled tumor protein (TCTP), tissue inhibitors of metalloproteinases-2 (TIMP-2), and triosephosphate isomerase (TPI), that were either increased or decreased simultaneously in conditioned media of both 1198 and 1170-I cells. Furthermore, levels of PGP9.5, TCTP, TIMP-2, and TPI were significantly increased not only in the conditioned media of both transformed cell lines when compared to those of BEAS-2B and 1799 cells, but also in plasmas and tissues from lung cancer patients when compared to those in normal controls. We suggest the PGP9.5, TCTP, TIMP-2, and TPI as promising candidates for lung cancer serum biomarkers.

Background: IL-4 can directly inhibit growth of several tumor cell types, but the molecular mechanism is not known. Results: IL-4 induces senescence by increasing p21 WAF1/CIP1 expression through STAT6 and p38 MAPK. Conclusion: STAT6 and p38 MAPK play important roles in senescence induction by IL-4. Significance: This is the first report of cellular senescence induction by IL-4 and the responsible mechanism.

The importance of proteostasis in preventing cellular senescence has been well recognized. However, the exact mechanism by which the loss of proteostasis or endoplasmic reticulum (ER) stress induces cellular senescence remains unclear. We report that ER stress mediates cellular senescence through the activating transcription factor (ATF)6α branch of the unfolded protein response (UPR). Cellular senescence was induced by the abrogation of neighbor of breast cancer (BRCA)1 gene (NBR1). NBR1 abrogation‐induced senescence was p53 dependent and observed in both transformed and nontransformed human cell lines: MCF‐7, Caki‐1, and MRC‐5. NBR1 bound to p38 MAPK, preferentially to an active form, and upon NBR1 abrogation, the activity of p38 increased. NADPH oxidase was activated in turn by p38, and the resulting oxidative stress triggered ER stress. It was found that ER stress mediated cellular senescence through the UPR sensor ATF6α. Knockdown of ATF6α prevented senescence, whereas ATF6α overexpression triggered it. The transcriptional activity of ATF6α was important. The ER stress‐ATF6α axis also mediated cellular senescence induced by H‐RasV12 overexpression and UV irradiation, suggesting a common role of this axis in senescence induction. In summary, we presented an evidence for the novel role of the ER stress‐ATF6α axis in cellular senescence.—Kim, H. S., Kim, Y., Lim, M. J., Park, Y.‐G., Park, S. I., Sohn, J. The p38‐activated ER stress‐ATF6α axis mediates cellular senescence. FASEB J. 33, 2422–2434 (2019). http://www.fasebj.org

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The cyclic adenosine monophosphate-response element (CRE)-transcription factor complex participates in the regulation of viral gene expression and pathologic processes caused by various viruses. The hepatitis B virus (HBV) enhancer I directs liver-specific transcription of viral genes and contains a CRE sequence (HBV-CRE); however, whether the HBV-CRE and CRE-binding protein (CREB) are required for the HBV life cycle remains to be determined. This study was designed to investigate the role of CREB in HBV replication and gene expression. Sequencecomparison analysis of 984 HBVs reported worldwide showed that the HBV-CRE sequence is highly conserved, indicating the possibility that it plays an important role in the HBV life cycle. The binding of CREB to the HBV-CRE site was markedly inhibited by oligonucleotides containing HBV-CRE and consensus CRE sequences in vitro and in vivo. The HBV promoter activity was demonstrated to be dependent upon the transactivation activity of CREB. Treatment with CRE decoy oligonucleotides reduced HBV promoter activity, and this was reversed by CREB overexpression. The levels of viral transcripts, DNA, and antigens were remarkably decreased in response to the overexpression of CREB mutants or treatment with the CRE decoy oligonucleotides, whereas enhancing CREB activity increased the levels of viral transcripts. In addition, introduction of a three-base mutation into the HBV-CRE led to a marked reduction in HBV messenger RNA synthesis. Conclusion: Taken together, our results demonstrate that both replication and gene expression of HBV require a functional CREB and HBV-CRE. We have also demonstrated that CRE decoy oligonucleotides and the overexpression of CREB mutants can effectively block the HBV life cycle, suggesting that interventions against CREB activity could provide a new avenue to treat HBV infection. (HEPATOLOGY 2008;48:361-373.) T he World Health Organization has reported that about 4 million people worldwide are acutely infected with hepatitis B virus (HBV) each year, and there are estimated to be 350 million chronic carriers worldwide. 1 The HBV is a major cause of acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. [1][2][3] The agents that are currently available for the treatment of chronic HBV infection are interferon-␣ and nucleos(t)ide analogs, such as lamivudine (L-2Ј,3Ј-dideoxy-thiacytidene), adefovir dipivoxil, and entecavir. 2-5 However, there are some limitations to these therapeutics: interferon-␣ has adverse effects, and nucleos(t)ide derivatives, although safe and efficacious, can lead to the emergence of resistant mutants. [2][3][4][5] Furthermore, none of these therapeutic agents can effectively eradicate the virus. 4,5 Studies on the regulatory mechanisms of HBV gene expression and replication are, therefore, necessary for the development of promising antiviral medications. Interventions against HBV include novel nucleic acid-based approaches employing antisense RNA and DNA, 6-8 ribozymes, 9,10 and RNA interference. [11][12][13]