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Inducible Expression System (inducible + expression_system)
Selected AbstractsDifferential effects of US2, US6 and US11 human cytomegalovirus proteins on HLA class,Ia and HLA-E expression: impact on target susceptibility to NK cell subsetsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2003Manuel Llano Abstract We compared in an inducible expression system the individual effect of US2, US6 and US11 human cytomegalovirus (HCMV) proteins on HLA-E and HLA class,Ia surface expression, assessing in parallel their influence on target susceptibility to NK cell clones. To this end, the RPMI,8866 B,lymphoma cell line (HLA-A2, HLA-A3, HLA-B7, HLA-Cw7, HLA-ER, HLA-EG) was stably cotransfected with the ecdysone receptor, together with the US sequences under the control of an ecdysone-inducible promoter. Biosynthesis of viral proteins was turned on by incubating transfectants with Ponasterone,A. US6 down-regulated expression of all class,I molecules, hampering target resistance to NK cell clones controlled by the CD94/NKG2A, KIR2DL2 and/or CD85j (ILT2 or LIR-1) inhibitory receptors. By contrast, US11 reduced the surface levels of class,Ia molecules but preserved HLA-E; this rendered US11+ cells sensitive to NK clones under the control of KIR2DL2 and/or CD85j, while their resistance to CD94/NKG2A+KIR2DL2, effector cells was maintained. US2 preserved as well HLA-E expression but selectively targeted class,Ia molecules; in fact, HLA-A and HLA-C allotypes were down-modulated whereas HLA-B7 remained unaltered. US2+ targets became sensitive to KIR2DL2+ cells but remained resistant to CD94/NKG2A+CD85j+ NK clones. The differential effects of US proteins on HLA class,Ia and HLA-E likely reflect the evolutionary adaptation of HCMV to counteract NK-mediated surveillance. [source] BRD7, a novel bromodomain gene, inhibits G1,S progression by transcriptionally regulating some important molecules involved in ras/MEK/ERK and Rb/E2F pathwaysJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2004Jie Zhou Bromodomain is a 110 amino acid domain. It is evolutionally conserved and is found in proteins strongly implicated in signal-dependent transcriptional regulation. BRD7 is a novel bromodomain gene and it is downexpressed in nasopharyngeal carcinoma (NPC) biopsies and cell lines; its function is poorly understood. In the present study, tet-on inducible expression system was used to investigate the role of BRD7 in cell growth and cell cycle progression. We found that ectopic expression of BRD7 in NPC cells inhibited cell growth and cell cycle progression from G1 to S. We further performed cell cycle cDNA array to screen potential transcriptional targets of BRD7 in cell cycle. Thirteen important signaling molecules, mainly implicated in ras/MEK/ERK and Rb/E2F pathways, were differentially expressed by induction of BRD7. Moreover, we observed that BRD7 could regulate the promoter activity of E2F3, one of its targets. Taken together, the present study indicated that BRD7 inhibited G1,S progression by transcriptionally regulating some important molecules involved in ras/MEK/ERK and Rb/E2F pathways and suggested that BRD7 may present a promising candidate of NPCÔ associated tumor suppressor gene. © 2004 Wiley-Liss, Inc. [source] A Drosophila melanogaster cell line (S2) facilitates post-genome functional analysis of receptors and ion channelsBIOESSAYS, Issue 11 2002Paula R. Towers The complete sequencing of the genome of the fruit fly Drosophila melanogaster offers the prospect of detailed functional analysis of the extensive gene families in this genetic model organism. Comprehensive functional analysis of family members is facilitated by access to a robust, stable and inducible expression system in a fly cell line. Here we show how the Schneider S2 cell line, derived from the Drosophila embryo, provides such an expression system, with the bonus that radioligand binding studies, second messenger assays, ion imaging, patch-clamp electrophysiology and gene silencing can readily be applied. Drosophila is also ideal for the study of new control strategies for insect pests since the receptors and ion channels that many new animal health drugs and crop protection chemicals target can be expressed in this cell line. In addition, many useful orthologues of human disease genes are emerging from the Drosophila genome and the study of their functions and interactions is another area for postgenome applications of S2 cell lines. BioEssays 24:1066,1073, 2002. © 2002 Wiley-Periodicals, Inc. [source] A tightly regulated inducible expression system utilizing the fim inversion recombination switchBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006Timothy S. Ham Abstract The fim inversion system of Escherichia coli (E. coli) can behave as a unidirectional switch in an efficient manner. We have developed a new expression system for E. coli, comprising the arabinose-inducible fimE gene and the fim invertible DNA segment containing a constitutively active promoter. In this system, the target gene is cloned with the promoter in the OFF orientation, resulting in no transcribed product. When induced by arabinose, the active promoter is switched to the ON orientation via FimE-catalyzed DNA inversion, and the gene is expressed. Our expression system exhibited very tightly controlled basal expression and high induced expression, with simple induction by inexpensive arabinose. These characteristics make our system suitable for large-scale expression or for production of toxic proteins. © 2006 Wiley Periodicals, Inc. [source] Dynamic assembly of chromatin complexes during cellular senescence: implications for the growth arrest of human melanocytic neviAGING CELL, Issue 4 2007Debdutta Bandyopadhyay Summary The retinoblastoma (RB)/p16INK4a pathway regulates senescence of human melanocytes in culture and oncogene-induced senescence of melanocytic nevi in vivo. This senescence response is likely due to chromatin modifications because RB complexes from senescent melanocytes contain increased levels of histone deacetylase (HDAC) activity and tethered HDAC1. Here we show that HDAC1 is prominently detected in p16INK4a -positive, senescent intradermal melanocytic nevi but not in proliferating, recurrent nevus cells that localize to the epidermal/dermal junction. To assess the role of HDAC1 in the senescence of melanocytes and nevi, we used tetracycline-based inducible expression systems in cultured melanocytic cells. We found that HDAC1 drives a sequential and cooperative activity of chromatin remodeling effectors, including transient recruitment of Brahma (Brm1) into RB/HDAC1 mega-complexes, formation of heterochromatin protein 1, (HP1,)/SUV39H1 foci, methylation of H3-K9, stable association of RB with chromatin and significant global heterochromatinization. These chromatin changes coincide with expression of typical markers of senescence, including the senescent-associated ,-galactosidase marker. Notably, formation of RB/HP1, foci and early tethering of RB to chromatin depends on intact Brm1 ATPase activity. As cells reached senescence, ejection of Brm1 from chromatin coincided with its dissociation from HP1,/RB and relocalization to protein complexes of lower molecular weight. These results provide new insights into the role of the RB pathway in regulating cellular senescence and implicate HDAC1 as a likely mediator of early chromatin remodeling events. [source] | ||||||||||