Home About us Contact
|
Home About us Contact | ||
|
|
||
Dependent Transcription (dependent + transcription)
Selected AbstractsMolecular cloning of the Matrix Gla Protein gene from Xenopus laevisFEBS JOURNAL, Issue 7 2002Functional analysis of the promoter identifies a calcium sensitive region required for basal activity To analyze the regulation of Matrix Gla Protein (MGP) gene expression in Xenopus laevis, we cloned the xMGP gene and its 5, region, determined their molecular organization, and characterized the transcriptional properties of the core promoter. The Xenopus MGP (xMGP) gene is organized into five exons, one more as its mammalian counterparts. The first two exons in the Xenopus gene encode the DNA sequence that corresponds to the first exon in mammals whereas the last three exons show homologous organization in the Xenopus MGP gene and in the mammalian orthologs. We characterized the transcriptional regulation of the xMGP gene in transient transfections using Xenopus A6 cells. In our assay system the identified promoter was shown to be transcriptionally active, resulting in a 12-fold induction of reporter gene expression. Deletional analysis of the 5, end of the xMGP promoter revealed a minimal activating element in the sequence from ,70 to ,36 bp. Synthetic reporter constructs containing three copies of the defined regulatory element delivered 400-fold superactivation, demonstrating its potential for the recruitment of transcriptional activators. In gel mobility shift assays we demonstrate binding of X. laevis nuclear factors to an extended regulatory element from ,180 to ,36, the specificity of the interaction was proven in competition experiments using different fragments of the xMGP promoter. By this approach the major site of factor binding was demonstrated to be included in the minimal activating promoter fragment from ,70 to ,36 bp. In addition, in transient transfection experiments we could show that this element mediates calcium dependent transcription and increasing concentrations of extracellular calcium lead to a significant dose dependent activation of reporter gene expression. [source] Thirty-kilodalton Tat-interacting protein suppresses tumor metastasis by inhibition of osteopontin transcription in human hepatocellular carcinoma,HEPATOLOGY, Issue 1 2008Jian Zhao It has been previously demonstrated that the 30-kDa Tat-interacting protein (TIP30) plays an important role in the suppression of hepatocarcinogenesis by acting as a tumor suppressor. Here we report that TIP30 suppresses metastasis of hepatocellular carcinoma (HCC) through inhibiting the transcription of osteopontin (OPN), a key molecule in the development of tumor metastasis. The expression of TIP30 messenger RNA was reverse to that of OPN messenger RNA in HCC cell lines. Ectopic expression of TIP30 greatly suppressed OPN expression, inhibited invasion of HCC cells through extracellular matrix (ECM) and adhesion with fibronectin in vitro, whereas down-regulation of TIP30 by RNA-mediated interference enhanced OPN expression and promoted metastatic abilities of HCC cells in vitro. Moreover, overexpression of TIP30 significantly inhibited the growth and lung metastases of HCC cells in nude mice. In contrast, down-regulation of TIP30 greatly promoted tumor cell growth and metastases in vivo. TIP30 repressed OPN transcription through interaction with Ets-1 and suppressed the transcriptional activity of Ets-1 and synergistic actions of Ets-1 and alkaline phosphatase-1. Thus, TIP30 may act as an Ets-1 modulator and inhibit tumor metastasis through abrogating Ets-1,dependent transcription. Moreover, expression of TIP30 was inversely associated with OPN expression in HCC tissue samples as detected by immunohistochemistry assay. Conclusion: Our results reveal a novel pathway by which OPN and possibly other Ets-1 target genes involved in tumor metastasis are regulated by TIP30 and elucidate a mechanism for metastasis promoted by TIP30 deficiency. (HEPATOLOGY 2008.) [source] Sp1 and krüppel-like factor family of transcription factors in cell growth regulation and cancerJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2001Adrian R. Black The Sp/KLF family contains at least twenty identified members which include Sp1-4 and numerous krüppel-like factors. Members of the family bind with varying affinities to sequences designated as ,Sp1 sites' (e.g., GC-boxes, CACCC-boxes, and basic transcription elements). Family members have different transcriptional properties and can modulate each other's activity by a variety of mechanisms. Since cells can express multiple family members, Sp/KLF factors are likely to make up a transcriptional network through which gene expression can be fine-tuned. ,Sp1 site'-dependent transcription can be growth-regulated, and the activity, expression, and/or post-translational modification of multiple family members is altered with cell growth. Furthermore, Sp/KLF factors are involved in many growth-related signal transduction pathways and their overexpression can have positive or negative effects on proliferation. In addition to growth control, Sp/KLF factors have been implicated in apoptosis and angiogenesis; thus, the family is involved in several aspects of tumorigenesis. Consistent with a role in cancer, Sp/KLF factors interact with oncogenes and tumor suppressors, they can be oncogenic themselves, and altered expression of family members has been detected in tumors. Effects of changes in Sp/KLF factors are context-dependent and can appear contradictory. Since these factors act within a network, this diversity of effects may arise from differences in the expression profile of family members in various cells. Thus, it is likely that the properties of the overall network of Sp/KLF factors play a determining role in regulation of cell growth and tumor progression. © 2001 Wiley-Liss, Inc. [source] The guanosine tetraphosphate (ppGpp) alarmone, DksA and promoter affinity for RNA polymerase in regulation of ,54 -dependent transcriptionMOLECULAR MICROBIOLOGY, Issue 3 2006Lisandro M. D. Bernardo Summary The RNA polymerase-binding protein DksA is a cofactor required for guanosine tetraphosphate (ppGpp)-responsive control of transcription from ,70 promoters. Here we present evidence: (i) that both DksA and ppGpp are required for in vivo,54 transcription even though they do not have any major direct effects on ,54 transcription in reconstituted in vitro transcription and ,-factor competition assays, (ii) that previously defined mutations rendering the housekeeping ,70 less effective at competing with ,54 for limiting amounts of core RNA polymerase similarly suppress the requirement for DksA and ppGpp in vivo and (iii) that the extent to which ppGpp and DksA affect transcription from ,54 promoters in vivo reflects the innate affinity of the promoters for ,54 -RNA polymerase holoenzyme in vitro. Based on these findings, we propose a passive model for ppGpp/DksA regulation of ,54 -dependent transcription that depends on the potent negative effects of these regulatory molecules on transcription from powerful stringently regulated ,70 promoters. [source] Mutational analysis of RsrA, a zinc-binding anti-sigma factor with a thiol,disulphide redox switchMOLECULAR MICROBIOLOGY, Issue 4 2001Mark S. B. Paget In the Gram-positive bacterium, Streptomyces coelicolor A3(2), expression of the thioredoxin system is modulated by a sigma factor called ,R in response to changes in the cytoplasmic thiol,disulphide status, and the activity of ,R is controlled post-translationally by an anti-sigma factor, RsrA. In vitro, the anti-sigma factor activity of RsrA, which contains seven cysteines, correlates with its thiol,disulphide redox status. Here, we investigate the function of RsrA in vivo. A constructed rsrA null mutant had very high constitutive levels of disulphide reductase activity and ,R -dependent transcription, confirming that RsrA is a negative regulator of ,R and a key sensor of thiol,disulphide status. Targeted mutagenesis revealed that three of the seven cysteines in RsrA (C11, C41 and C44) were essential for anti-sigma factor activity and that a mutant RsrA protein containing only these three cysteines was active and still redox sensitive in vivo. We also show that RsrA is a metalloprotein, containing near-stoichiometric amounts of zinc. On the basis of these data, we propose that a thiol,disulphide redox switch is formed between two of C11, C41 and C44, and that all three residues play an essential role in anti-sigma factor activity in their reduced state, perhaps by acting as ligands for zinc. Unexpectedly, rsrA null mutants were blocked in sporulation, probably as a consequence of an increase in the level of free ,R. [source] Inhibition of protein kinase CK2 leads to a modulation of androgen receptor dependent transcription in prostate cancer cellsTHE PROSTATE, Issue 2 2007Claudia Götz Abstract BACKGROUND The androgen receptor (AR) mediates the biological responses of androgens in the prostate gland. In prostate cancer, this pathway is often deregulated and causes an uncontrolled proliferation. METHODS The current study focuses on the effects of an inhibition of protein kinase CK2 on the AR-mediated transcription in LNCaP prostate cancer cells. We used chemical inhibitors of CK2 as well as dominant-negative kinase mutants to downregulate the CK2 activity. We determined the effects of the inhibition by Western blot analysis of endogenous target genes of the AR as well as by reporter assays. RESULTS We found that inhibition of CK2 led to a downregulation of the AR-dependent transcription. Moreover, the amount of the AR protein decreased significantly. CONCLUSION According to the fact that AR pathways are involved in the development and progression of prostate cancer, the ability to modulate AR function should provide an alternative basis for the development of new cancer therapies. Prostate © 2006 Wiley-Liss, Inc. [source] | |||||||||||||