ABSTRACT
The human BK polyomavirus (BKPyV) is latent in the kidneys of most adults, but can be reactivated in immunosuppressed states, such as following renal transplantation. If left unchecked, BK polyomavirus nephropathy (PyVAN) and possible graft loss may result from viral destruction of tubular epithelial cells and interstitial fibrosis. When coupled with regular post-transplant screening, immunosuppression reduction has been effective in limiting BKPyV viremia and the development of PyVAN. Antiviral drugs that are safe and effective in combating BKPyV have not been identified but would be a benefit in complementing or replacing immunosuppression reduction. The present study explores inhibition of the host DNA damage response (DDR) as an antiviral strategy. Immunohistochemical and immunofluorescent analyses of PyVAN biopsies provide evidence for stimulation of a DDR in vivo. DDR pathways were also stimulated in vitro following BKPyV infection of low-passage human renal proximal tubule epithelial cells. The role of Chk1, a protein kinase known to be involved in the replication stress-induced DDR, was examined by inhibition with the small molecule LY2603618 and by siRNA-mediated knockdown. Inhibition of Chk1 resulted in decreased replication of BKPyV DNA and viral spread. Activation of mitotic pathways was associated with the reduction in BKPyV replication. Chk1 inhibitors that are found to be safe and effective in clinical trials for cancer should also be evaluated for antiviral activity against BKPyV.
Subject(s)
BK Virus/genetics , Checkpoint Kinase 1/metabolism , Polyomavirus Infections/drug therapy , BK Virus/pathogenicity , Cells, Cultured , Checkpoint Kinase 1/physiology , DNA Damage/physiology , DNA Repair/physiology , Humans , Kidney/pathology , Kidney/virology , Kidney Transplantation , Phenylurea Compounds/pharmacology , Polyomavirus Infections/genetics , Polyomavirus Infections/immunology , Pyrazines/pharmacology , Tumor Virus Infections/drug therapy , Tumor Virus Infections/genetics , Virus Replication/drug effects , Virus Replication/physiologyABSTRACT
An indazole based series of glucocorticoid receptor agonists is reported. The SAR exploration of this scaffold yielded compounds with nanomolar affinity for the glucocorticoid receptor with indications of selectivity for the preferred transrepression mechanism; in vivo efficacy was observed in the mouse LPS induced TNFalpha model for compound 28.
Subject(s)
Anti-Inflammatory Agents/chemistry , Indazoles/chemistry , Receptors, Glucocorticoid/agonists , Animals , Anti-Inflammatory Agents/chemical synthesis , Anti-Inflammatory Agents/pharmacology , Indazoles/chemical synthesis , Indazoles/pharmacology , Mice , Receptors, Glucocorticoid/metabolism , Tumor Necrosis Factor-alpha/metabolismABSTRACT
The introduction of an aryl ring onto the 4-position of the C-6 benzyl amino group of the Cdk inhibitor roscovitine (2), maintained the potent Cdk inhibition demonstrated by roscovitine (2) as well as greatly improving the antiproliferative activity. A series of C-6 biarylmethylamino derivatives was prepared addressing modifications on the C-6 biaryl rings, N-9 and C-2 positions to provide compounds that displayed potent cytotoxic activity against tumor cell lines. In particular, derivative 21h demonstrated a >750-fold improvement in the growth inhibition of HeLa cells compared to roscovitine (2).
Subject(s)
Antineoplastic Agents/pharmacology , Cyclin-Dependent Kinases/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Purines/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Proliferation/drug effects , Drug Design , Drug Screening Assays, Antitumor , HeLa Cells , Humans , Molecular Structure , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Purines/chemical synthesis , Purines/chemistry , Roscovitine , Stereoisomerism , Structure-Activity RelationshipABSTRACT
C-6 Biarylmethylamino purine derivatives of roscovitine (1) inhibit cyclin dependent kinases and demonstrate potent antiproliferative activity. Replacement of the aryl rings of the C-6 biarylmethylamino group with heterobiaryl rings has provided compounds with significantly improved activity. In particular, derivatives 18 g and 9 c demonstrated 1000-fold and 1250-fold improvements, respectively, in the growth inhibition of HeLa cells compared to roscovitine (1).
Subject(s)
Antineoplastic Agents/pharmacology , Cyclin-Dependent Kinases/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Purines/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Proliferation/drug effects , Drug Design , Drug Screening Assays, Antitumor , HeLa Cells , Humans , Molecular Structure , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Purines/chemical synthesis , Purines/chemistry , Roscovitine , Stereoisomerism , Structure-Activity RelationshipABSTRACT
A series of A-ring and E-ring analogues of the natural product luotonin A, a known topoisomerase I poison, was evaluated for growth inhibition in human carcinoma and leukemia cell lines. Rational design of structures was based on analogues of the related alkaloid camptothecin, which has been demonstrated to exert cytotoxic effects by the same mechanism of action. When compared to luotonin A, several compounds exhibited an improved topoisomerase I-dependent growth inhibition of a human leukemia cell line.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Pyrroles/chemical synthesis , Pyrroles/pharmacology , Quinones/chemical synthesis , Quinones/pharmacology , Topoisomerase I Inhibitors , Topoisomerase II Inhibitors , Cell Line, Tumor , Cell Proliferation/drug effects , Humans , Magnetic Resonance Spectroscopy , Spectrometry, Mass, Electrospray IonizationABSTRACT
The roles of the HIV1 protein Vpr in virus replication and pathogenesis remain unclear. Expression of Vpr in dividing cells causes cell cycle arrest in G(2). Vpr also facilitates low titer infection of terminally differentiated macrophages, enhances transcription, promotes apoptosis, and targets cellular uracil N-glycosylase for degradation. Using co-immunoprecipitation and tandem mass spectroscopy, we found that HIV1 Vpr engages a DDB1- and cullin4A-containing ubiquitin-ligase complex through VprBP/DCAF1. HIV2 Vpr has two Vpr-like proteins, Vpr and Vpx, which cause G(2) arrest and facilitate macrophage infection, respectively. HIV2 Vpr, but not Vpx, engages the same set of proteins. We further demonstrate that the interaction between Vpr and the ubiquitin-ligase components as well as further assembly of the ubiquitin-ligase are necessary for Vpr-mediated G(2) arrest. Our data support a model in which Vpr engages the ubiquitin ligase to deplete a cellular factor that is required for cell cycle progression into mitosis. Vpr, thus, functions like the HIV1 proteins Vif and Vpu to usurp cellular ubiquitin ligases for viral functions.
Subject(s)
Carrier Proteins/physiology , Cullin Proteins/physiology , DNA-Binding Proteins/physiology , G2 Phase , Gene Products, vpr/physiology , Ubiquitin-Protein Ligases/physiology , Cells, Cultured , Humans , Immunoprecipitation , Uracil-DNA Glycosidase/metabolismABSTRACT
BACKGROUND: Simian Virus 40 (SV40) infection of growth-arrested monkey kidney cells stimulates S phase entry and the continued synthesis of both viral and cellular DNA. Infected cells can attain total DNA contents as high as DNA Index, DI = 5.0-6.0 (10-12C), with host cell DNA representing 70-80% of the total. In this study, SV40-infected and uninfected control cells were compared to determine whether continued DNA replication beyond DI = 2.0 was associated with rebinding of the minichromosome maintenance (MCM) hexamer, the putative replicative helicase, to chromatin. METHOD: Laser scanning cytometry was used to measure the total expression per cell and the chromatin/matrix-association of two MCM subunits in relation to DNA content. RESULTS: MCM2 and MCM3 proteins that were associated with the chromatin/matrix fraction in G1 phase of both uninfected and SV40-infected cells were gradually released during progression through S phase. However, in SV40-infected cells that progressed beyond DI = 2.0, chromatin/matrix-associated MCM2 and MCM3 remained at the low levels observed at the end of S phase. Rereplication was not preceded by an obvious rebinding of MCM proteins to chromatin, as was observed in G1 phase. CONCLUSIONS: The rereplication of host cell DNA in the absence of the reassociation of MCM proteins with chromatin indicates that SV40 infection induces a novel mechanism of licensing cellular DNA replication.
Subject(s)
Cell Cycle Proteins/metabolism , Cell Nucleus/metabolism , Nuclear Proteins/metabolism , S Phase/physiology , Animals , Antigens, Viral, Tumor/metabolism , Blotting, Western , Cell Cycle/physiology , Cell Cycle Proteins/genetics , Cell Line , Chlorocebus aethiops , Chromatin/metabolism , DNA/genetics , DNA/metabolism , Eukaryotic Cells/metabolism , Eukaryotic Cells/virology , Immunohistochemistry , Laser Scanning Cytometry , Microscopy, Fluorescence , Minichromosome Maintenance Complex Component 2 , Nuclear Matrix/metabolism , Nuclear Proteins/genetics , Phosphorylation , Protein Binding , Simian virus 40/growth & development , Simian virus 40/immunology , Time Factors , Virus Replication/physiologyABSTRACT
Lytic infection of African green monkey kidney (CV-1) cells by simian virus 40 (SV40) is characterized by stimulation of DNA synthesis leading to bypass of mitosis and replication of cellular and viral DNA beyond a 4C DNA content. To define mechanisms underlying the absence of mitosis, the expression levels of upstream regulatory molecules of mitosis-promoting factor (MPF) were compared in parallel synchronized cultures of SV40-infected and uninfected CV-1 cells. The DNA replication/damage checkpoint kinase Chk1 was phosphorylated in both uninfected and SV40-infected cultures arrested at G(1)/S by mimosine, consistent with checkpoint activation. Following release of uninfected cultures from G(1)/S, Chk1 phosphorylation was lost even though Chk1 protein levels were retained. In contrast, G(1)/S-released SV40-infected cultures exhibited dephosphorylation of Chk1 in S phase, followed by an increase in Chk1 phosphorylation coinciding with entry of infected cells into >G(2). Inhibitors of Chk1, UCN-01 and caffeine, induced mitosis and abnormal nuclear condensation and increased the protein kinase activity of MPF in SV40-infected CV-1 cells. These results demonstrate that SV40 lytic infection triggers components of a DNA damage checkpoint pathway. In addition, chemical inhibition of Chk1 activity suggests that Chk1 contributes to the absence of mitosis during SV40 lytic infection.
Subject(s)
Protein Kinases/physiology , Simian virus 40/physiology , Viral Proteins/physiology , Alkaloids/pharmacology , Animals , Caffeine/pharmacology , Cell Line , Checkpoint Kinase 1 , Chlorocebus aethiops , Enzyme Activation , Enzyme Inhibitors/pharmacology , Flow Cytometry , Fluorescent Antibody Technique , Mitosis/drug effects , Nocodazole/pharmacology , Phosphorylation , Protein Kinase Inhibitors , Staurosporine/analogs & derivativesABSTRACT
Livers from wild-type and p53-deficient mice were analyzed for the expression of cell-cycle regulatory proteins in an attempt to determine the mechanism for the increased proliferation of liver cells in p53-deficient mice associated with enhanced susceptibility to aflatoxin-induced liver cancer. The most striking difference found was a significant reduction of the cyclin-dependent kinase inhibitor p27(kip1) in the livers of 3-mo-old p53-/- mice, whereas only small changes were found in the expression of cyclins, cyclin-dependent kinases, and the inhibitors p21(cip1) and p16(ink4a). Relative to wild-type liver, the amounts of p27(kip1) mRNA were reduced at both 1 and 3 mo, whereas the levels of p27(kip1) protein were decreased only at 3 mo. These results identify an uncharacterized link between the expression of p53 and p27(kip1) that may involve both transcriptional and post-transcriptional regulation and allow hepatocytes to continue to proliferate after 3 wk of age. We postulate that this increased proliferation leads to increased susceptibility to aflatoxin-induced hepatocarcinogenesis.