ABSTRACT
p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe.
Subject(s)
HIV-1/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Adult , Apoptosis/genetics , Apoptosis/physiology , Ataxia Telangiectasia Mutated Proteins , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , DNA Damage/genetics , DNA Damage/physiology , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Giant Cells/metabolism , HeLa Cells , Humans , Immunohistochemistry , Intracellular Signaling Peptides and Proteins/genetics , Male , Mitosis/genetics , Mitosis/physiology , Phosphorylation , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , RNA Interference , Tumor Suppressor Proteins/genetics , Tumor Suppressor Proteins/metabolism , Tumor Suppressor p53-Binding Protein 1 , env Gene Products, Human Immunodeficiency Virus/metabolism , env Gene Products, Human Immunodeficiency Virus/physiologyABSTRACT
Promyelomonocytic leukemia (PML) is a prominent oncosuppressor whose inactivation is involved in the pathogenesis of hematological and epithelial cancers. Here, we report that PML aggregated in nuclear bodies in syncytia elicited by the envelope glycoprotein complex (Env) of human immunodeficiency virus-1 (HIV-1) in vitro. PML aggregation occurred after the fusion of nuclei (karyogamy) within syncytia but before the apoptotic program was activated. The aggregation of PML was detectable in syncytia present in the brain or lymph nodes from patients with HIV-1 infection, as well as in a fraction of blood leukocytes, correlating with viral status. Using a range of specific inhibitors of PML (the oncogenic PML/RARalpha fusion product or specific small interfering RNAs), we demonstrated that, in Env-elicited syncytia, PML was required for activating phosphorylation of ataxia telangiectasia mutated (ATM), which colocalized with PML in nuclear bodies, in a molecular complex that also involved topoisomerase IIbeta-binding protein 1. PML knockdown thus inhibited the ATM-dependent DNA damage response that culminates in the activation of p53, p53-dependent transcription of pro-apoptotic genes and cell death. Infection of CD4-expressing cells with HIV-1 also induced syncytial apoptosis, which could be suppressed by inhibiting PML. Altogether, these data indicate that PML activation is a critical early event that participates in the apoptotic demise of HIV-1-elicited syncytia.
Subject(s)
Apoptosis , HIV-1 , Nuclear Proteins/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolism , env Gene Products, Human Immunodeficiency Virus/metabolism , Ataxia Telangiectasia Mutated Proteins , Cell Cycle Proteins/metabolism , DNA-Binding Proteins/metabolism , Giant Cells/virology , HeLa Cells , Humans , Promyelocytic Leukemia Protein , Protein Serine-Threonine Kinases/metabolism , RNA, Small Interfering , Signal Transduction , Tumor Suppressor Protein p53/metabolismABSTRACT
Self-focusing and self-defocusing of light in two-wave mixing are investigated experimentally. Amplification and self-focusing are measured as functions of the frequency shift between signal and pump beams. A frequency dependence is found in Kramers-Kronig form, as is plausible by the analogy of photorefractive amplification and laser amplification. Reversal of the external dc field on the material or a change in the frequency shift between the signal and pump beams is found to change self-focusing to self-defocusing.
ABSTRACT
The minimal metabolism-inhibiting concentrations (MMC) of 11 antibiotics were determined for 40 strains each of M. hominis and U. urealyticum using a terminal color change broth method. All strains were recovered in 1990. Resistance to tetracycline (MMC greater than 8 mg/l) was found for 12.5% of strains of M. hominis and U. urealyticum, as compared with 5% in 1985. Rokitamycin was the most active macrolide against M. hominis (MMC 90: 0.06 mg/l). U. urealyticum strains were susceptible to all the macrolides tested, with the greatest activities being seen for rokitamycin and clarithromycin (MMC 90: 0.06 mg/l and 0.12 mg/l respectively). Sparfloxacin was the most active quinolone against both species. Human clinical trials designed to evaluate these new molecules for the treatment of mycoplasmal and ureaplasmal genital infections are warranted.
