Cellular kinases incorporated into HIV-1 particles: passive or active passengers?

Phosphorylation is one of the major mechanisms by which the activities of protein factors can be regulated. Such regulation impacts multiple key-functions of mammalian cells, including signal transduction, nucleo-cytoplasmic shuttling, macromolecular complexes assembly, DNA binding and regulation of enzymatic activities to name a few. To ensure their capacities to replicate and propagate efficiently in their hosts, viruses may rely on the phosphorylation of viral proteins to assist diverse steps of their life cycle. It has been known for several decades that particles from diverse virus families contain some protein kinase activity. While large DNA viruses generally encode for viral kinases, RNA viruses and more precisely retroviruses have acquired the capacity to hijack the signaling machinery of the host cell and to embark cellular kinases when budding. Such property was demonstrated for HIV-1 more than a decade ago. This review summarizes the knowledge acquired in the field of HIV-1-associated kinases and discusses their possible function in the retroviral life cycle

Insect cell endocytosis of chikungunya virus adapted to Aedes albopictus, a mosquito recently introduced into southern France

International audienc

Refined study of the interaction between HIV-1 p6 late domain and ALIX

The interaction between the HIV-1 p6 late budding domain and ALIX, a class E vacuolar protein sorting factor, was explored by using the yeast two-hybrid approach. We refined the ALIX binding site of p6 as being the leucine triplet repeat sequence (Lxx)4 (LYPLTSLRSLFG). Intriguingly, the deletion of the C-terminal proline-rich region of ALIX prevented detectable binding to p6. In contrast, a four-amino acid deletion in the central hinge region of p6 increased its association with ALIX as shown by its ability to bind to ALIX lacking the proline rich domain. Finally, by using a random screening approach, the minimal ALIX391–510 fragment was found to specifically interact with this p6 deletion mutant. A parallel analysis of ALIX binding to the late domain p9 from EIAV revealed that p6 and p9, which exhibit distinct ALIX binding motives, likely bind differently to ALIX. Altogether, our data support a model where the C-terminal proline-rich domain of ALIX allows the access of its binding site to p6 by alleviating a conformational constraint resulting from the presence of the central p6 hinge

HIV-1-associated PKA acts as a cofactor for genome reverse transcription

BACKGROUND: Host cell proteins, including cellular kinases, are embarked into intact HIV-1 particles. We have previously shown that the Cα catalytic subunit of cAMP-dependent protein kinase is packaged within HIV-1 virions as an enzymatically active form able to phosphorylate a synthetic substrate in vitro (Cartier et al. J. Biol. Chem. 278:35211 (2003)). The present study was conceived to investigate the contribution of HIV-1-associated PKA to the retroviral life cycle. RESULTS: NL4.3 viruses were produced from cells cultured in the presence of PKA inhibitors H89 (H89-NL4.3) or Myr-PKI (PKI-NL4.3) and analyzed for viral replication. Despite being mature and normally assembled, and containing expected levels of genomic RNA and RT enzymatic activity, such viruses showed poor infectivity. Indeed, infection generated reduced amounts of strong-strop minus strand DNA, while incoming RNA levels in target cells were unaffected. Decreased cDNA synthesis was also evidenced in intact H89-NL4.3 and PKI-NL4.3 cell free particles using endogenous reverse transcription (ERT) experiments. Moreover, similar defects were reproduced when wild type NL4.3 particles preincubated with PKA inhibitors were subjected to ERT reactions. CONCLUSIONS: Altogether, our results indicate that HIV-1-associated PKA is required for early reverse transcription of the retroviral genome both in cell free intact viruses and in target cells. Accordingly, virus-associated PKA behaves as a cofactor of an intraviral process required for optimal reverse transcription and for early post-entry events

VSV-G pseudotyping rescues HIV-1 CA mutations that impair core assembly or stability

<p>Abstract</p> <p>Background</p> <p>The machinery of early HIV-1 replication still remains to be elucidated. Recently the viral core was reported to persist in the infected cell cytoplasm as an assembled particle, giving rise to the reverse transcription complex responsible for the synthesis of proviral DNA and its transport to the nucleus. Numerous studies have demonstrated that reverse transcription of the HIV-1 genome into proviral DNA is tightly dependent upon proper assembly of the capsid (CA) protein into mature cores that display appropriate stability. The functional impact of structural properties of the core in early replicative steps has yet to be determined.</p> <p>Results</p> <p>Here, we show that infectivity of HIV-1 mutants bearing S₁₄₉A and S₁₇₈A mutations in CA can be efficiently restored when pseudotyped with vesicular stomatitis virus envelope glycoprotein, that addresses the mutant cores through the endocytic pathway rather than by fusion at the plasma membrane. The mechanisms by which these mutations disrupt virus infectivity were investigated. S₁₄₉A and S₁₇₈A mutants were unable to complete reverse transcription and/or produce 2-LTR DNA. Morphological analysis of viral particles and <it>in vitro </it>uncoating assays of isolated cores demonstrated that infectivity defects resulted from disruption of the viral core assembly and stability for S₁₄₉A and S₁₇₈A mutants, respectively. Consistent with these results, both mutants failed to saturate TRIM-antiviral restriction activity.</p> <p>Conclusion</p> <p>Defects generated at the level of core assembly and stability by S₁₄₉A and S₁₇₈A mutations are sensitive to the way of delivery of viral nucleoprotein complexes into the target cell. Addressing CA mutants through the endocytic pathway may compensate for defects generated at the reverse transcription/nuclear import level subsequent to impairment of core assembly or stability.</p

Uracil DNA Glycosylase 2 negatively regulates HIV-1 LTR transcription

Numerous cellular factors belonging to the DNA repair machineries, including RAD18, RAD52, XPB and XPD, have been described to counteract human immunodeficiency virus type 1 (HIV-1) replication. Recently, Uracil DNA glycosylase 2 (UNG2), a major determinant of the uracil base excision repair pathway, was shown to undergo rapid proteasome-dependent degradation following HIV-1 infection. However, the specific role of intracellular UNG2 depletion during the course of HIV-1 infection is not clearly understood. Our study shows for the first time that overexpression of UNG2 inhibits HIV-1 replication. We demonstrate that this viral inhibition is correlated with a marked decrease in transcription efficiency as shown by monitoring HIV-1 LTR promoter activity and quantification of HIV-1 RNA levels. Interestingly, UNG2 inhibits LTR activity when stimulated by Tat transactivator or TNFα, while barely affected using Phorbol ester activation. Mutational analysis of UNG2 indicates that antiviral activity may require the integrity of the UNG2 catalytic domain. Altogether, our data indicate that UNG2 is likely to represent a new host defense factor specifically counteracted by HIV-1 Vpr. The molecular mechanisms involved in the UNG2 antiviral activity still remain elusive but may rely on the sequestration of specific cellular factor(s) critical for viral transcription

Observatoire Scientifique en Appui à la GEstion de la Santé sur un territoire (OSAGE-S)

Dans le contexte « environnement-santé », l’équipe interdisciplinaire (biologistes, médecins, épidémiologistes, modélisateurs, écologues, géographes, informaticiens) qui travaille sur la dynamique de maladies infectieuses dans le Sud-Est asiatique, propose de mettre en commun la connaissance qu’elle a des agents biologiques pathogènes et des processus qui interviennent dans les milieux et les sociétés et de partager expériences de terrain, de laboratoire, clinique pour aborder les questions de recherche, de suivi des maladies et de gestion de la santé. Pour ce faire, l’idée d’une plateforme intégrative a été avancée et nous a permis de décliner la proposition de mise en œuvre d’un Observatoire Scientifique en Appui à la GEstion de la Santé sur un territoire (OSAGE-S). Les prémices de ce travail sont d’une part d’ordre générique et épistémologique : ils explicitent formellement la formule « environnement-santé » pour y positionner le pathosystème, l’environnement et l’observatoire ; d’autre part d’ordre opérationnel par explicitation du concept d’observatoire en appui à la gestion de la Santé. Par la suite nous illustrerons nos propos autour d’OSAGE-S, à partir d’une étude de cas, la maladie du Chikungunya en Indonésie.Within the “Health and Environment” framework, a group of scientists in disciplinary fields as diverse as biology, medical sciences, modelling, ecology, geography, computer sciences, are collaborating to study the dynamics of infectious diseases in Southeast Asia. In this paper they propose to pool their knowledge on biological pathogens, environment and societies and to share their field, laboratory and clinical expertise to address questions on research, disease monitoring and health management. An integrative platform has been suggested and organised in order to implement a Scientific Observatory (OSAGE-S), dedicated to supporting Health Management in a Territory. The first part of this work addresses generic and epistemological questions, formally explicits the formula “Health and Environment” in order to relate it to concepts such as « pathological system », « environment » and « observatory » ; the second part relates to further operational issues for the observatory concept dedicated to the support of Health management. Thereafter we illustrate our proposition with a case study, the Chikungunya disease in Indonesia