Project description:p16INK4A inhibits the CDK4/6 kinases and is therefore an important cell cycle regulator. Accumulation of p16INK4A in response to oncogenic transformation leads to cellular senescence and it is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of cellular oxidative stress and therefore could potentially be regulated by redox signaling, which is a form of signal transduction that is mediated by the reversible oxidation of cysteine-thiol side chains in proteins. We found that oxidation of the single cysteine residue in p16INK4A in human cells occurs under relatively mild oxidizing conditions and that this leads to disulfide dependent dimerization. p16INK4A is a well-characterized all alpha-helical protein, but we find that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-β sheet structure, and typical dimensions found in electron microscopy. We find that p16INK4A amyloid formation abolishes its function as a CDK4/6 inhibitor in human cells. Taken together, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils.
Project description:To investigate the specific roles of HDAC2 in the development of gastric cancer, we employed large-scale gene expression analysis to identify the molecular signature that may affect enabling characteristics of cancer cells. Differentially expressed genes were analyzed on the MKN-1 cells transfected with HDAC2 shRNAs, and recapitulated molecular signatures that related to hallmarks of cancer. DNA methylation of p16INK4a promoter region was assessed by methylation specific polymerase chain reaction. Recruiting the HDAC2 at the p16INK4a promoter was identified using chromatin immunoprecipitation assay. RNA interference-mediated protein knockdown method was used to investigate oncogenic potential of HDAC2 in in vitro and in vivo gastrocarcinogenesis of MKN-1 cells. RNA interference-mediated protein knockdown versus mock treatment
Project description:This 89-node Boolean model of mammalian growth factor signaling can reproduce oscillations in PI3K signaling in cycling cells, and links these oscillations to the regulatory networks that drive each phase of cell cycle progression, as well as apoptosis. It builds on our previous work on modeling cell cycle progression as the interaction of two linked multi-stable switches (Deritei et al, Sci Rep 6:21957, 2016) and extends it to capture the role of Plk1 in cell cycle progression.
The resulting model reproduces the following experimentally documented cell behaviors:
— cyclic PI3K/AKT1 activity in dividing cells, which remain in sync with the cell cycle
— apoptosis in response to prolonged mitosis or mitotic catastrophe
— four distinct, experimentally documented cell fates caused by Plk1 inhibition, depending on the
timing of Plk1 loss; namely, G2 arrest, mitotic catastrophe, premature anaphase and chromosome mis-segregation leading to aneuploidy, and failure to complete cytokinesis following telophase, which can lead to genome duplication
— failure of cytokinesis and accumulation of binucleate telophase cells driven by hyperactive PI3K, hyperactive Ak1, or FoxO inhibition.
— the effect of a large number of knockdown / forced activation mutations
— PI3K degradation in response to high PI3K activation is driven by the Neddl4 ubiquitin ligase activated by PLCγ, while its re-synthesis requires nuclear re-accumulation of FoxO3.
— The degradation/re-synthesis cycle of PI3K occurs twice per division cycle, synchronized by Plk1-mediated inhibition of FoxO3 during metaphase/anaphase.
— Cells in which PI3K is inhibited after the start of DNA synthesis can nevertheless pre-commit to another cell cycle in the presence of saturating growth stimulation (passing the restriction point in late metaphase), albeit at lower rates than wild-type cells.
— Cell cycle defects in response to PI3K/Ak1 over-activation or FoxO knockdown are driven by a loss of Plk1 in telophase.
Project description:Endosomal Toll-like receptors (TLRs) play an important role in the etiology of systemic autoimmune diseases such as SLE, where DNA- and RNA-associated autoantigens activate autoreactive B cells through TLR9- and TLR7-dependent pathways, respectively. Nevertheless, TLR9-deficient autoimmune prone mice develop more severe clinical disease, while TLR7-deficient and TLR7/9-double deficient autoimmune-prone mice develop less severe disease. To determine whether the regulatory activity of TLR9 is B cell intrinsic, we have now directly compared the functional properties of autoantigen activated WT, TLR9-deficient and TLR7-deficient B cells, in an experimental system where proliferation depends on BCR/TLR co-engagement. In vitro, TLR9-deficient cells are less dependent on survival factors for a sustained proliferative response than either WT or TLR7-deficient cells. The TLR9-deficient cells also preferentially differentiate toward the plasma cell lineage, as indicated by expression of CD138, sustained expression of IRF4, and other molecular markers of plasma cells. In vivo, autoantigen-activated TLR9-deficient cells give rise to greater numbers of autoantibody producing cells. Our results identify distinct roles for TLR7 and TLR9 in the differentiation of autoreactive B cells that explain the capacity of TLR9 to limit, and TLR7 to promote, the clinical features of SLE. AM14 WT, Tlr7-/-, Tlr9-/- and Tlr7/9-/- B cells were stimulated with PL2-3 for 0, 6, 24, and 42 hours, for a total of 16 samples.
Project description:Currently approved inhibitors of the PD-1/PD-L1 pathway represent a major advance for the treatment of lung cancers, yet they are ineffective in a majority of patients due to lack of pre-existing T cell reactivity. Here we show that a TLR9 agonist delivered by inhalation is able to prime T cell responses against poorly immunogenic lung tumors and to complement the effects of PD-1 blockade. Treatment with inhaled TLR9 agonist causes profound remodeling in tumor-bearing lungs, leading to formation of tertiary lymphoid structures adjacent to the tumors, CD8+ T cell infiltration into the tumors, dendritic cell expansion and antibody production. Inhaled TLR9 agonist treatment increased the pool of functional PD-1lowT-bethigh effector CD8+ T in tumor-bearing lungs. We show by transcriptional profiling, that the effector CD8+ T cells generated by inhaled TLR9 agonist treatment are licensed by PD-1 blockade to become highly functional CTL, leading to a durable rejection of both lung tumors and tumor lesions outside the lungs. CD4+ T cells activated in response to inhaled TLR9 play a critical role in this process by controlling the proliferation, preventing exhaustion, and guiding the differentiation of optimally functional CTL. This study characterizes a strategy to apply localized TLR9 stimulation to a tumor type not accessible for direct injection, a strategy that may expand the therapeutic potential of PD-1 blockade in non-small cell lung cancer. the scope of this experiment was to profile the gene expression of effector CD8 T cells from tumor bearing lungs treated by different drug regimen. Overall design: Gene expression was performed on purified CD44+CD8+ effector T cells from 4T1 tumor-bearing lungs treated with the indicated treatment regimen (group names reflect treatment). Saline-CTRL (n=5), SD-101 (n=6), SD-101+anti-PD-1 (n=5), SD-101+anti-PD-1+a-CD4 (n=4)
Project description:Background: Eukaryotic cells must inhibit re-initiation of DNA replication at each of the thousands of origins in their genome because re-initiation events can generate genomic alterations with extraordinary frequency. To minimize the probability of re-initiation from so many origins, cells use a battery of regulatory mechanisms that reduce the activity of replication initiation proteins. Given the global nature of these mechanisms, it has been presumed that all origins are inhibited identically. However, transiently disabling these mechanisms causes replication origins to re-initiate with diverse efficiencies, which do not correlate with known differences in the efficiency or timing of origin initiation during normal DNA replication. These observations suggest an additional local layer of replication control that can differentially influence how re-initiation is regulated at distinct origins. Principal Findings: We have identified novel genetic elements that are necessary for preferential re-initiation of two origins and sufficient to confer preferential re-initiation on heterologous origins when the control of re-initiation is partially deregulated. The elements do not enhance the S phase timing or efficiency of adjacent origins and thus are specifically acting as re-initiation promoters (RIPs). We have mapped the two RIPs to ~60bp AT rich sequences that act in a distance- and sequence-dependent manner. During the induction of re-replication, Mcm2-7 re-associates both with origins that preferentially re-initiate and origins that do not, suggesting that the RIP elements can overcome a block to re-initiation imposed after Mcm2-7 associates with origins. Conclusions/Significance: We have uncovered a local level of control in the block to re-initiation. This local control creates a complex genomic landscape of re-replication potential that is revealed when global mechanisms preventing re-replication are peeled away. Hence, if re-replication does contribute to genomic alterations, as has been speculated for cancer cells, some regions of the genome may be more susceptible to these alterations than others. 142 array CGH experiments are presented. Each experiment is done in experimental replicate. Cells grown as described in Richardson CD and Li JJ PLoS Genetics 2014. Ch1 samples taken from replicating (S phase) or re-replicating (M phase + 3/6 hour induced). Ch2 samples taken from M phase arrested DNA.
Project description:Analyze the effect of TLR9 deficiency on immue cell function at the gene expression level. Our hypothesis was that TLR9 deficiency promotes CD73 expression in T cells thus regulates autoimmune diabetes development in NOD mice. Sorted TCRb+ cells were pooled from several mice for furhter RNA extraction and cRNA labeling.
Project description:To analyze the effect of Exportin-5 expression on the MEF cells in cell cycle re-entry phase, we have employed whole genome microarray expression profiling on the MEF cells in cell cycle re-entry phase with and without down regulation of Exportin-5 gene. Mouse MEF cells were transfected with 60nM of siRNA targeting either Exportin-5 or negative control, and incubated for 12 hours. After incubation, cells were starved with DMEM containing 0.2% FCS for 48 hours and re-fed with DMEM containing 20%FCS for 24 hours, along with second siRNA transfection. Two independant expreiments were preformed.