The Experts below are selected from a list of 11217 Experts worldwide ranked by ideXlab platform
Robert Horowits - One of the best experts on this subject based on the ideXlab platform.
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role of nonmuscle myosin iib and n Rap in cell spreading and myofibril assembly in primary mouse cardiomyocytes
Cytoskeleton, 2008Co-Authors: Shajia Lu, Robert HorowitsAbstract:We investigated the role of nonmuscle myosin heavy chain (NMHC) IIB in cultured embryonic mouse cardiomyocytes by specific knockdown using RNA interference. NMHC IIB Protein levels decreased 90% compared with mock-transfected cells by 3 days post transfection. NMHC IIB knockdown resulted in a slow decrease in N-Rap Protein levels over 6 days with no change in N-Rap transcript levels. N-Rap is a scaffold for α-actinin and actin assembly during myofibrillogenesis, and we quantitated myofibril accumulation by morphometric analysis of α-actinin organization. Between 3 and 6 days, NMHC IIB knockdown was accompanied by the abolishment of cardiomyocyte spreading. During this period the rate of myofibril accumulation steadily decreased, correlating with the slowly decreasing levels of N-Rap. Between 6 and 8 days NMHC IIB and N-Rap Protein levels recovered, and cardiomyocyte spreading and myofibril accumulation resumed. Inhibition of proteasome function using MG132 led to accumulation of excess N-Rap, and the secondary decrease in N-Rap that otherwise accompanied NMHC IIB knockdown was abolished. The results show that NMHC IIB knockdown led to decreased N-Rap levels through proteasome-mediated degradation. Furthermore, these Proteins have distinct functional roles, with NMHC IIB playing a role in cardiomyocyte spreading and N-Rap functioning in myofibril assembly.
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targeted disruption of n Rap gene function by rna interference a role for n Rap in myofibril organization
Cytoskeleton, 2006Co-Authors: Ashwini S Dhume, Shajia Lu, Robert HorowitsAbstract:N-Rap is a muscle-specific Protein concentrated in myofibril precursors during sarcomere assembly and at intercalated disks in adult heart. We used RNA interference to achieve a targeted decrease in N-Rap transcript and Protein levels in primary cultures of embryonic mouse cardiomyocytes. N-Rap transcript levels were decreased by ∼70% within 2 days following transfection with N-Rap specific siRNA. N-Rap Protein levels steadily decreased over several days, reaching ∼50% of control levels within 6 days. N-Rap Protein knockdown was associated with decreased myofibril assembly, as assessed by α-actinin organization into mature striations. Transcripts encoding N-Rap binding Proteins associated with assembling or mature myofibrils, such as α-actinin, Krp1, and muscle LIM Protein, were expressed at normal levels during N-Rap Protein knockdown, and α-actinin and Krp-1 Protein levels were also unchanged. Transcripts encoding muscle myosin heavy chain and nonmuscle myosin heavy chain IIB were also expressed at relatively normal levels. However, decreased N-Rap Protein levels were associated with dramatic changes in the encoded myosin Proteins, with muscle myosin heavy chain levels increasing and nonmuscle myosin heavy chain IIB decreasing. N-Rap transcript and Protein levels recovered to normal by days 6 and 7, respectively, and the changes in myofibril organization and myosin heavy chain isoform levels were reversed. Our data indicate that we can achieve transient N-Rap Protein knockdown using the RNA interference technique and that α-actinin organization into myofibrils in cardiomyocytes is closely linked to N-Rap Protein levels. Finally, N-Rap Protein levels regulate the balance between nonmuscle myosin IIB and muscle myosin by post-trancriptional mechanisms. Cell Motil. Cytoskeleton 2006. Published 2006 Wiley-Liss, Inc.
Gary S Hayward - One of the best experts on this subject based on the ideXlab platform.
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lytic replication associated Protein Rap encoded by kaposi sarcoma associated herpesvirus causes p21cip 1 mediated g1 cell cycle arrest through ccaat enhancer binding Protein α
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Qi Qun Tang, Honglin Chen, Colette Aprhys, Christopher Farrell, Jianmeng Chen, Masahiro Fujimuro, Daniel M Lane, Gary S HaywardAbstract:Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic DNA virus that causes Kaposi sarcoma and AIDS-related primary effusion lymphoma (PEL). Here we show that KSHV lytic cycle replication in PEL cells induces G1 cell cycle arrest, presumably to facilitate the progression of viral DNA replication. Expression of a KSHV-encoded early lytic Protein referred to as Rap or K8 is induced within 12–24 h after the onset of lytic cycle induction in host PEL cells, and coincides with increased levels of both the endogenous C/EBPα and p21CIP-1 Proteins in the nucleus of the same cells. The KSHV Rap Protein binds to C/EBPα in vitro and stimulates C/EBPα-induced expression from both the C/EBPα and p21 promoters in cotransfected cells. A recombinant adenovirus expressing the Rap Protein induced the expression of both the C/EBPα and p21 Proteins in primary human fibroblasts, and flow cytometric analysis revealed a dramatic inhibition of G1 to S cell cycle progression in the same cells. All of these effects were abolished in cells that lack C/EBPα or by deletion of the basic/leucine zipper region in Rap that interacts with C/EBPα. Therefore, C/EBPα is essential for the p21-mediated inhibition of G1 to S-phase progression by Rap in KSHV-infected host cells.
Shajia Lu - One of the best experts on this subject based on the ideXlab platform.
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role of nonmuscle myosin iib and n Rap in cell spreading and myofibril assembly in primary mouse cardiomyocytes
Cytoskeleton, 2008Co-Authors: Shajia Lu, Robert HorowitsAbstract:We investigated the role of nonmuscle myosin heavy chain (NMHC) IIB in cultured embryonic mouse cardiomyocytes by specific knockdown using RNA interference. NMHC IIB Protein levels decreased 90% compared with mock-transfected cells by 3 days post transfection. NMHC IIB knockdown resulted in a slow decrease in N-Rap Protein levels over 6 days with no change in N-Rap transcript levels. N-Rap is a scaffold for α-actinin and actin assembly during myofibrillogenesis, and we quantitated myofibril accumulation by morphometric analysis of α-actinin organization. Between 3 and 6 days, NMHC IIB knockdown was accompanied by the abolishment of cardiomyocyte spreading. During this period the rate of myofibril accumulation steadily decreased, correlating with the slowly decreasing levels of N-Rap. Between 6 and 8 days NMHC IIB and N-Rap Protein levels recovered, and cardiomyocyte spreading and myofibril accumulation resumed. Inhibition of proteasome function using MG132 led to accumulation of excess N-Rap, and the secondary decrease in N-Rap that otherwise accompanied NMHC IIB knockdown was abolished. The results show that NMHC IIB knockdown led to decreased N-Rap levels through proteasome-mediated degradation. Furthermore, these Proteins have distinct functional roles, with NMHC IIB playing a role in cardiomyocyte spreading and N-Rap functioning in myofibril assembly.
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targeted disruption of n Rap gene function by rna interference a role for n Rap in myofibril organization
Cytoskeleton, 2006Co-Authors: Ashwini S Dhume, Shajia Lu, Robert HorowitsAbstract:N-Rap is a muscle-specific Protein concentrated in myofibril precursors during sarcomere assembly and at intercalated disks in adult heart. We used RNA interference to achieve a targeted decrease in N-Rap transcript and Protein levels in primary cultures of embryonic mouse cardiomyocytes. N-Rap transcript levels were decreased by ∼70% within 2 days following transfection with N-Rap specific siRNA. N-Rap Protein levels steadily decreased over several days, reaching ∼50% of control levels within 6 days. N-Rap Protein knockdown was associated with decreased myofibril assembly, as assessed by α-actinin organization into mature striations. Transcripts encoding N-Rap binding Proteins associated with assembling or mature myofibrils, such as α-actinin, Krp1, and muscle LIM Protein, were expressed at normal levels during N-Rap Protein knockdown, and α-actinin and Krp-1 Protein levels were also unchanged. Transcripts encoding muscle myosin heavy chain and nonmuscle myosin heavy chain IIB were also expressed at relatively normal levels. However, decreased N-Rap Protein levels were associated with dramatic changes in the encoded myosin Proteins, with muscle myosin heavy chain levels increasing and nonmuscle myosin heavy chain IIB decreasing. N-Rap transcript and Protein levels recovered to normal by days 6 and 7, respectively, and the changes in myofibril organization and myosin heavy chain isoform levels were reversed. Our data indicate that we can achieve transient N-Rap Protein knockdown using the RNA interference technique and that α-actinin organization into myofibrils in cardiomyocytes is closely linked to N-Rap Protein levels. Finally, N-Rap Protein levels regulate the balance between nonmuscle myosin IIB and muscle myosin by post-trancriptional mechanisms. Cell Motil. Cytoskeleton 2006. Published 2006 Wiley-Liss, Inc.
Peter L Graumann - One of the best experts on this subject based on the ideXlab platform.
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induction of plasmid conjugation in bacillus subtilis is bistable and driven by a direct interaction of a Rap phr quorum sensing system with a master repressor
Journal of Biological Chemistry, 2015Co-Authors: Thomas C Rosch, Peter L GraumannAbstract:Abstract Conjugation of plasmid pLS20 from Bacillus subtilis is limited to a time window between early and late exponential growth. Genetic evidence has suggested that pLS20-encoded Protein RcoLS20 represses expression of a large conjugation operon, while Rap Protein RapLS20 relieves repression. We show that RapLS20 is a true antirepressor Protein that forms dimers in vivo and in vitro, and that directly binds to the repressor Protein RcoLS20, in a 1:1 stoichiometry. We provide evidence that RapLS20 binds to the helix-turn-helix containing domain of RcoLS20 in vivo, likely obstructing DNA-binding of RcoLS20 as seen in competitive DNA binding experiments. The activity of RapLS20 in turn is counteracted by the addition of the cognate PhrLS20 peptide, which directly binds to the Rap Protein and presumably induces a conformational change of the antirepressor. Thus, a Rap Protein acts directly as an antirepressor Protein during regulation of plasmid conjugation, turning on conjugation, and is counteracted by the PhrLS20 peptide, which by analogy to known Rap/Phr systems is secreted and taken back up into the cells, mediating cell density-driven regulation. Finally, we show that this switch-like process establishes a population-heterogeneity, where up to 30% of the cells induce transcription of the conjugation operon.
Marta Perego - One of the best experts on this subject based on the ideXlab platform.
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Rap phosphatase of virulence plasmid pxo1 inhibits bacillus anthracis sporulation
Journal of Bacteriology, 2006Co-Authors: Cristina Bongiorni, Ricarda Stoessel, Dorinda Shoemaker, Marta PeregoAbstract:This study shows that the Bacillus anthracis pXO1 virulence plasmid carries a Rap-Phr system, BXA0205, which regulates sporulation initiation in this organism. The BXA0205Rap Protein was shown to dephosphorylate the Spo0F response regulator intermediate of the phosphorelay signal transduction system that regulates the initiation of the developmental pathway in response to environmental, metabolic, and cell cycle signals. The activity of the Rap Protein was shown to be inhibited by the carboxy-terminal pentapeptide generated through an export-import processing pathway from the associated BXA0205Phr Protein. Deregulation of the Rap activity by either overexpression or lack of the Phr pentapeptide resulted in severe inhibition of sporulation. Five additional Rap-Phr encoding systems were identified on the chromosome of B. anthracis, one of which, BA3790-3791, also affected sporulation initiation. The results suggest that the plasmid-borne Rap-Phr system may provide a selective advantage to the virulence of B. anthracis.