Human T-cell leukemia virus type-1 (HTLV-1) is the etiological agent of adult T-cell leukemia (ATL). The trans-activator protein Tax of HTLV-1 plays crucial roles in leukemogenesis by promoting proliferation of virus-infected cells through activation of growth-promoting genes. However, critical target genes are yet to be elucidated.
View Article and Find Full Text PDFHuman T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma. The oncogene product Tax of HTLV-I is thought to play crucial roles in leukemogenesis by promoting proliferation of the virus-infected cells through activation of growth-promoting genes. These genes code for growth factors and their receptors, cytokines, cell adhesion molecules, growth signal transducers, transcription factors and cell cycle regulators.
View Article and Find Full Text PDFThe TFDP1 gene codes for the heterodimeric partner DP1 of the transcription factor E2F. E2F, principal target of the tumor suppressor pRB, plays central roles in cell proliferation by activating a group of growth-related genes. E2F also mediates tumor suppression by activating tumor suppressor genes such as ARF, an upstream activator of the tumor suppressor p53, when deregulated from pRB upon oncogenic changes.
View Article and Find Full Text PDFThe transcription factor E2F, the principal target of the tumor suppressor pRB, plays crucial roles in cell proliferation and tumor suppression. In almost all cancers, pRB function is disabled, and E2F activity is enhanced. To specifically target cancer cells, trials have been undertaken to suppress enhanced E2F activity to restrain cell proliferation or selectively kill cancer cells, utilizing enhanced E2F activity.
View Article and Find Full Text PDFMitochondrial damage is caused by changes in the micro-environmental conditions during tumor progression. Cancer cells require mechanisms for mitochondrial quality control during this process; however, how mitochondrial integrity is maintained is unclear. Here we show that E2F3d, a previously unidentified E2F3 isoform, mediates hypoxia-induced mitophagy in cancer cells.
View Article and Find Full Text PDFThe transcription factor E2F plays crucial roles in cell proliferation and tumor suppression by activating growth-related genes and pro-apoptotic tumor suppressor genes, respectively. It is generally accepted that E2F binds to target sequences with its heterodimeric partner DP. Here we show that, while knockdown of DP1 expression inhibited ectopic E2F1- or adenovirus E1a-induced expression of the CDC6 gene and cell proliferation, knockdown of DP1 and DP2 expression did not affect ectopic E2F1- or E1a-induced expression of the tumor suppressor ARF gene, an upstream activator of the tumor suppressor p53, activation of p53 or apoptosis.
View Article and Find Full Text PDFThe physical properties of the extracellular matrix (ECM), such as stiffness, are involved in the determination of the characteristics of cancer cells, including chemotherapy sensitivity. Resistance to chemotherapy is often linked to dysfunction of tumor suppressor p53; however, it remains elusive whether the ECM microenvironment interferes with p53 activation in cancer cells. Here, we show that, in MCF-7 breast cancer cells, extracellular stiffness influences p53 activation induced by the antitumor drug doxorubicin.
View Article and Find Full Text PDFIn cancer treatment, specifically targeting cancer cells is important for optimal therapeutic efficacy. One strategy is to utilize a cancer specific promoter to express a cytotoxic gene or a viral gene required for replication. In this approach, the therapeutic window is dependent on the relative promoter activity in cancer cells versus normal cells.
View Article and Find Full Text PDFThe transcription factor E2F plays crucial roles in tumor suppression by activating pro-apoptotic genes such as the tumor suppressor ARF. The regulation of the ARF gene is distinct from that of growth-related E2F targets, in that it is specifically activated by deregulated E2F activity, induced by over-expression of E2F or forced inactivation of pRB, but not by physiological E2F activity induced by growth stimulation. The phosphatidyl inositol 3 kinase (PI3K) pathway was reported to suppress expression of some atypical pro-apoptotic genes by over-expressed E2F1.
View Article and Find Full Text PDFThe heterodimeric transcription factor E2F1-DP1 plays crucial roles in coordinating gene expression during G/S cell cycle progression. For transcriptional activation, the transactivation domain (TAD) of E2F1 is known to interact with the TATA-binding protein of TFIID and the p62 subunit of TFIIH. It is generally believed that DP1 facilitates E2F1 binding to target DNA and does not possess a TAD.
View Article and Find Full Text PDFCell migration is a highly dynamic process that plays pivotal roles in both physiological and pathological processes. We have previously reported that p130Cas supports cell migration through the binding to Src as well as phosphorylation-dependent association with actin retrograde flow at focal adhesions. However, it remains elusive how phosphorylated Cas interacts with actin cytoskeletons.
View Article and Find Full Text PDFCell Mol Life Sci
November 2015
Cancer cells possess unique characteristics such as invasiveness, the ability to undergo epithelial-mesenchymal transition, and an inherent stemness. Cell morphology is altered during these processes and this is highly dependent on actin cytoskeleton remodeling. Regulation of the actin cytoskeleton is, therefore, important for determination of cell fate.
View Article and Find Full Text PDFSkeletal muscle degeneration is a complication arising from a variety of chronic diseases including advanced cancer. Pro-inflammatory cytokine TNF-α plays a pivotal role in mediating cancer-related skeletal muscle degeneration. Here, we show a novel function for retinoblastoma protein (Rb), where Rb causes sarcomeric disorganization.
View Article and Find Full Text PDFActin dynamics are implicated in various cellular processes, not only through the regulation of cytoskeletal organization, but also via the control of gene expression. In the present study we show that the Src family kinase substrate p130Cas (Cas is Crk-associated substrate) influences actin remodelling and concomitant muscle-specific gene expression, thereby regulating myogenic differentiation. In C2C12 myoblasts, silencing of p130Cas expression by RNA interference impaired F-actin (filamentous actin) formation and nuclear localization of the SRF (serum-response factor) co-activator MAL (megakaryocytic acute leukaemia) following the induction of myogenic differentiation.
View Article and Find Full Text PDFThe IkappaB kinase (IKK)-NF-kappaB pathway plays a critical role in oncogenesis. Recently, we have shown that p53 regulates glucose metabolism through the IKK-NF-kappaB pathway and that, in the absence of p53, the positive feedback loop between IKK-NF-kappaB and glycolysis has an integral role in oncogene-induced cell transformation. Here, we demonstrate that IKKbeta, a component of the IKK complex, was constitutively modified with O-linked beta-N-acetyl glucosamine (O-GlcNAc) in both p53-deficient mouse embryonic fibroblasts (MEFs) and transformed human fibroblasts.
View Article and Find Full Text PDFBiochem Biophys Res Commun
July 2008
NF-kappaB plays an important role in oncogenesis. Recently, we have demonstrated that loss of p53 function enhances DNA binding and transcriptional activities of NF-kappaB via IKKalpha and IKKbeta, and that glycolysis, activated by NF-kappaB, has an integral role in oncogene-induced cell transformation. Here, we show that ectopically expressed p53 induces acetylation and phosphorylation at Ser 536 of p65, an NF-kappaB component, and enhances DNA-binding activity of NF-kappaB.
View Article and Find Full Text PDFCancer cells use aerobic glycolysis preferentially for energy provision and this metabolic change is important for tumour growth. Here, we have found a link between the tumour suppressor p53, the transcription factor NF-kappaB and glycolysis. In p53-deficient primary cultured cells, kinase activities of IKKalpha and IKKbeta and subsequent NF-kappaB activity were enhanced.
View Article and Find Full Text PDFThe activity of E2F transcription factors plays a crucial role in mammalian cell-cycle progression and is controlled by physical association with the pocket proteins (pRb and its related p107 and p130). The E2F1 promoter, which contains two overlapping E2F-binding sites, is activated at the G1/S transition in an E2F-dependent manner. Mutational experiments have shown that the distal E2F-binding site on the E2F1 promoter is required for transcriptional repression in the G0 phase, whereas the proximal E2F-binding site contributes to transcriptional activation at the G1/S boundary.
View Article and Find Full Text PDFE2FBP1/DRIL1 is an AT-rich interaction domain DNA-binding protein and is ubiquitously expressed in various tissues. It has been shown that Bright, the mouse orthologue of E2FBP1/DRIL1, exhibits sequence-specific DNA binding and regulates immunoglobulin transcription. Here we show a novel connection between E2FBP1/DRIL1 and the p53 tumor suppressor, a key regulator of growth arrest or apoptosis in response to cellular stress.
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