TGF-β induces PML SUMOylation, degradation and PML nuclear body disruption.

ProMyelocytic Leukemia (PML) protein is essential for the formation of nuclear matrix-associated organelles named PML nuclear bodies (NBs) that act as a platform for post-translational modifications and protein degradation. PML NBs harbor transiently and permanently localized proteins and are associated with the regulation of several cellular functions including apoptosis. There are seven PML isoforms, six nuclear (PMLI-VI) and one cytoplasmic (PMLVII), which are encoded by a single gene via alternative RNA splicing.

Differential effects of SUMO1 and SUMO3 on PKR activation and stability.

Double-stranded RNA (dsRNA)-dependent protein kinase (PKR) is a serine/threonine kinase that exerts its own phosphorylation and the phosphorylation of the α subunit of the protein synthesis initiation factor eIF-2α. PKR was identified as a target of SUMOylation and the triple PKR-SUMO deficient mutant on Lysine residues K60-K150-K440 has reduced PKR activity. We report that SUMO1 and SUMO3 expression exert differential effects on PKR localization, activation and stability.

Small Ubiquitin-like Modifier Alters IFN Response.

IFNs orchestrate immune defense through induction of hundreds of genes. Small ubiquitin-like modifier (SUMO) is involved in various cellular functions, but little is known about its role in IFN responses. Prior work identified STAT1 SUMOylation as an important mode of regulation of IFN-γ signaling.

Requirement of PML SUMO interacting motif for RNF4- or arsenic trioxide-induced degradation of nuclear PML isoforms.

PML, the organizer of nuclear bodies (NBs), is expressed in several isoforms designated PMLI to VII which differ in their C-terminal region due to alternative splicing of a single gene. This variability is important for the function of the different PML isoforms. PML NB formation requires the covalent linkage of SUMO to PML.

PML positively regulates interferon gamma signaling.

PML, also known as TRIM19, belongs to the family encoding a characteristic RBCC/TRIM motif comprising several cysteine-rich zinc-binding domains (RING and B-boxes) and a coiled-coil domain. The RBCC domain and the covalent modification of PML by the small ubiquitin-like modifier (SUMO) are required for PML localization within the nuclear bodies (NBs). Analysis of PML(-/-) mice provided evidence for a physiological role of PML in apoptosis.

SUMOylation promotes PML degradation during encephalomyocarditis virus infection.

The promyelocytic leukemia (PML) protein is expressed in the diffuse nuclear fraction of the nucleoplasm and in matrix-associated structures, known as nuclear bodies (NBs). PML NB formation requires the covalent modification of PML to SUMO. The noncovalent interactions of SUMO with PML based on the identification of a SUMO-interacting motif within PML seem to be required for further recruitment within PML NBs of SUMOylated proteins.

Resistance to rabies virus infection conferred by the PMLIV isoform.

Various reports implicate PML and PML nuclear bodies (NBs) in an intrinsic antiviral response targeting diverse cytoplasmic replicating RNA viruses. PML conjugation to the small ubiquitin-like modifier (SUMO) is required for its localization within NBs. PML displays antiviral effects in vivo, as PML deficiency renders mice more susceptible to infection with the rhabdovirus vesicular stomatitis virus (VSV).

Role of SUMO in RNF4-mediated promyelocytic leukemia protein (PML) degradation: sumoylation of PML and phospho-switch control of its SUMO binding domain dissected in living cells.

Promyelocytic leukemia protein (PML) is a tumor suppressor acting as the organizer of subnuclear structures called PML nuclear bodies (NBs). Both covalent modification of PML by the small ubiquitin-like modifier (SUMO) and non-covalent binding of SUMO to the PML SUMO binding domain (SBD) are necessary for PML NB formation and maturation. PML sumoylation and proteasome-dependent degradation induced by the E3 ubiquitin ligase, RNF4, are enhanced by the acute promyelocytic leukemia therapeutic agent, arsenic trioxide (As2O3).

[Antiviral activities of interferon and PML pathway].

Discovered in 1957 for their antiviral properties, interferons (IFNs) are a growing cytokine family with diverse biological activities including antitumor and immunoregulatory activities. IFN are classified in three types I, II and III. They bind to different specific cell receptors and induce via the Jak/Stat pathway the expression of more than 300 genes, the products of which are believed to mediate their biological effects.

Evidence against a direct cytotoxic effect of alpha interferon and zidovudine in HTLV-I associated adult T cell leukemia/lymphoma.

The combination of the anti-viral agents, zidovudine (AZT) and interferon-alpha (IFN), is a potent treatment of HTLV-I-associated adult T cell leukemia/lymphoma (ATL). In this study we investigate the possible mechanism of action of this combination by examining several cellular parameters including cell proliferation, cell cycle distribution and apoptosis. The ATL-derived T cell lines HuT-102 and MT-2 served as models.

Arsenic trioxide and interferon-alpha synergize to induce cell cycle arrest and apoptosis in human T-cell lymphotropic virus type I-transformed cells.

Human T-cell lymphotropic virus type I (HTLV-I) is the causative agent of adult T-cell leukemia/lymphoma (ATL). ATL is an aggressive proliferation of mature activated T cells associated with a poor prognosis. The combination of the antiviral agents, zidovudine (AZT) and interferon (IFN), is a potent treatment of ATL.

Effects of serotonin and melanin on in vitro HIV-1 infection.

In this article, we describe the effect of indoleamines: serotonin (5-HT) and synthetic soluble melanin, on the multiplication of HIV-1 in T4 lymphocytic cell lines. The results show that viral production is increased when infected CEM-11 cells are incubated with 5-HT (10(-7) M and 10(-8) M) for 72 hours, whereas at higher doses (10(-3) M and 10(-4) M), there is an inhibition of viral multiplication. As well, when infected CEM cells were cultured in the presence of 5-HT at 10(-4) M, during 15 days, virus production, syncytia formation and cytolytic effect were drastically inhibited.

Cell abnormalities associated with human papillomavirus-induced squamous intraepithelial cervical lesions. Multivariate data analysis.

One hundred ninety-six cervical scrapings were obtained for simultaneous research of cell abnormalities in Papanicolaou smears and detection of genital human papillomavirus (HPV) genotypes by polymerase chain reaction in extracted DNA from each clinical sample. The samples described by six discriminant cytologic parameters, and a synthetic HPV-presence/absence parameter provided an efficient matrix for multiple correspondence analysis. This statistical analysis displayed a plurality of HPV-related cell abnormalities in squamous intraepithelial lesions, and a high correspondence between HPV infection and the presence of multinucleated squamous cells, morphologically transformed keratinocytes (dyskaryotic cells), koilocytes, and cellular changes related to epithelial maturation.

Detection of IAP related transcripts in normal and transformed rat cells.

Intracisternal A-particles (IAP) genes in variable copy number exist in all rodent species studied. Expression is highly repressed in murine normal cells except in embryonic and transformed cells. We searched for IAP related sequences expression in another rodent species cells.

In vitro induction of early mouse embryo intracisternal particles (epsilon particles) in cultured cell lines.

The experimental induction of epsilon particles, retrovirus-like structures corresponding to the small IA particles of the mouse, was studied by electron microscopy in rodent-cultured cell lines. Among the chemicals tested, only IdUr was shown to be an effective inducer, but not cycloheximide, puromycin , deoxy-fluorouracil or 5-azacytidine. However, only two mouse-derived cell lines: Ki-BALB and FG 10, among 27 cell lines of mouse, rat and mink origins tested, expressed epsilon particles upon IdUr treatment.

Electron microscopic characterisation of retrovirus and retrovirus-like particles induced by demethylating agents (5-azacytidine and 5-azadeoxycytidine) in Syrian hamster (Mesocricetus auratus) cells.

In a framework of a study on retrovirus expression in Syrian hamster (mesocricetus auratus), three cell lines were examined by electron microscopy. As we had previously demonstrated the efficacy of demethylating drug in activating the formation of retroviral particles, we used 5-azacytidine to activate endogenous retrovirus expression. Proceeding to a more detailed survey we were able to observe various types of retrovirions.

Effects of in vitro infection of mouse glial and neuroblastoma cells with the scrapie agent.

Mouse glial and neuroblastoma cells were infected with the mouse adapted strains C506 and 139A of scrapie agent. Lysates of the in vitro infected cells (from the 3rd to the 16th passage) intracerebrally inoculated into CD-1 mice, caused the development of a neurological disease, with characteristic signs of scrapie. Morphological changes in scrapie-infected neural cells were observed after about fifteen in vitro passages.

Regulation of intracisternal A particles in mouse teratocarcinoma cells: involvement of DNA methylation in transcriptional control.

The methylation state of Intracisternal A Particle (IAP) genes in mouse teratocarcinoma cell lines has been investigated as an approach to study the regulation of the expression of these particles. Treatment of the cells with the methylation inhibitor 5-azacytidine induces the production of the particles in all the cells; the induction is particularly striking in an embryonal carcinoma cell line which is normally devoid of IAPs. The induction is accompanied by decrease in DNA methylation as demonstrated by using the methylation sensitive isoschizomer enzymes MspI and HpaII.

Intracisternal A particles: RNA expression and DNA methylation in murine teratocarcinoma cell lines.

Two main intracisternal-A-particle-specific RNA species (29 to 30S and 35 to 36S) are variably expressed in particle-producing and particle-nonproducing murine teratocarcinoma cell lines. An analysis of DNA methylation patterns after hybridization with an intracisternal-A-particle-specific probe showed an apparent direct correlation between DNA methylation and RNA expression. However, when the methylation assay was performed on the excised intracisternal A particle genes in one of the particle-rich cell lines (PCC6), some undermethylated sequences were detectable.

In vitro propagation of the scrapie agent. I. Transformation of mouse glia and neuroblastoma cells after infection with the mouse-adapted scrapie strain c-506.

Seven cell lines including glia cells from mouse brains and mouse neuroblastoma cells were infected with the mouse-adapted scrapie strain c-506. During the early in vitro passages, a stimulation of growth was already observed but cellular morphology and differentiation did not alter. Later on, after 12-16 passages, six of the seven infected lines displayed cell proliferation and morphological alterations, suggesting an in vitro morphological transformation.

[Effect of 5-azacytidine on the expression of intracisternal A and epsilon particles in various mouse cell lines].

5-Azacytidine treatment of several Mouse cell lines cultured in vitro induces the synthesis of a high number of intracisternal A particles. This induction could be related to the demethylation effect of the 5-Azacytidine. On the contrary, the epsilon intracisternal particles are not activated by 5-Azacytidine.