Early steps of retrovirus replicative cycle

During the last two decades, the profusion of HIV research due to the urge to identify new therapeutic targets has led to a wealth of information on the retroviral replication cycle. However, while the late stages of the retrovirus life cycle, consisting of virus replication and egress, have been partly unraveled, the early steps remain largely enigmatic. These early steps consist of a long and perilous journey from the cell surface to the nucleus where the proviral DNA integrates into the host genome. Retroviral particles must bind specifically to their target cells, cross the plasma membrane, reverse-transcribe their RNA genome, while uncoating the cores, find their way to the nuclear membrane and penetrate into the nucleus to finally dock and integrate into the cellular genome. Along this journey, retroviruses hijack the cellular machinery, while at the same time counteracting cellular defenses. Elucidating these mechanisms and identifying which cellular factors are exploited by the retroviruses and which hinder their life cycle, will certainly lead to the discovery of new ways to inhibit viral replication and to improve retroviral vectors for gene transfer. Finally, as proven by many examples in the past, progresses in retrovirology will undoubtedly also provide some priceless insights into cell biology

Le soutien parental à l'autonomie et la santé mentale des enfants: un regard sur le rôle de la hiérarchie culturelle

Thèse de doctorat présentée en vue de l'obtention du doctorat en psychologie - recherche intervention, option psychologie clinique (Ph.D)Parmi les déterminants environnementaux, les pratiques parentales représentent le facteur de prédiction de la santé mentale des enfants le plus largement accepté dans la littérature (Holte et al., 2014). Il est intéressant que le soutien à l’autonomie (SA) représente l’une des trois composantes clés du parentage optimal. Alors que les bienfaits de la satisfaction du besoin d’autonomie seraient, selon la théorie de l’autodétermination (TAD ; Ryan et Deci, 2017), universels, des différences fondamentales existent en ce qui concerne les pratiques parentales à travers les cultures (Lehman et al., 2004). Étant donné que la relation parent-enfant représente un type de relation hiérarchique, la variable de la hiérarchie culturelle (HC) s’avère particulièrement pertinente. La HC met l’accent sur la reconnaissance et le respect de l’autorité (Schwartz, 1994, 2008). Composée de deux études empiriques, la présente thèse tente de faire un pas de plus dans la réflexion concernant la généralisation interculturelle des bénéfices du SA parental. L’étude 1 repose sur deux banques de données transversales, recueillies auprès de participants présentant une large variabilité culturelle. L’objectif était d’explorer les associations entre la HC, le SA parental et les indicateurs d’ajustement psychosocial des jeunes et d’examiner si la HC joue un rôle modérateur dans l’association entre le SA parental et l’ajustement psychosocial des jeunes. Les résultats indiquent que plus le niveau de HC des parents est faible, plus leur niveau de SA est élevé. Alors que le SA parental est associé positivement aux indicateurs de bien-être (p.ex., satisfaction de vie) et négativement aux difficultés (p.ex., symptômes), les résultats n’ont révélé aucune modération par la HC, à l’exception de la relation entre le SA parental et la régulation autonome des adolescents. L’étude 2 a utilisé des données provenant d’une étude expérimentale mesurant les effets de l’atelier parental How to talk so kids will listen & listen so kids will talk (Faber & Mazlish, 1980; 2000) afin d’évaluer si le niveau de HC des parents modère les effets (ou l’absence d’effets) de l’atelier sur les pratiques parentales et la santé mentale des enfants. Dans l’ensemble, les résultats suggèrent un impact généralement indifférencié sur les pratiques parentales et sur la santé mentale des enfants, et ce, en ayant réalisé une multitude de tests (effets sur le SA, l’affiliation, et le cadre des parents, rapportés par les parents et les enfants, de même que le bien-être et les symptômes des enfants). Les effets précédemment documentés de l’atelier ne diffèrent donc généralement pas selon l’identité ethnique des parents. Parmi l’ensemble des tests réalisés, la seule exception concerne le SA tel que perçu par les enfants. En somme, les deux études ont porté sur le rôle potentiellement modérateur de la HC dans la relation entre les pratiques parentales soutenant l’autonomie et divers indicateurs de santé mentale chez les jeunes. De manière générale, les patrons de résultats suggèrent que les jeunes dont les parents favorisent davantage leur autonomie ont tendance à présenter de meilleurs niveaux d’ajustement psychosocial et ce, indépendamment du niveau de HC lié à l’ethnicité de leurs parents. De plus, les résultats ont montré que l’atelier évalué a un impact similaire sur les pratiques parentales et la santé mentale des enfants, quelle que soit l'ethnicité des parents qui y ont participé. Ces résultats soutiennent de manière générale la position de la TAD sur les bénéfices universels du SA.Among the environmental determinants, parental practices represent the most widely accepted predictor of children's mental health in the literature (Holte et al., 2014). Interestingly, autonomy support (AS) represents one of the three key components of optimal parenting. While the benefits of satisfying the need for autonomy are believed to be universal according to Self-Determination Theory (SDT; Ryan & Deci, 2017), fundamental differences exist in parental practices across cultures (Lehman et al., 2004). Given that the parent-child relationship represents a hierarchical type of relationship, the cultural hierarchy variable (CH) is particularly relevant. CH emphasizes the recognition and respect for authority (Schwartz, 1994, 2008). Comprised of two empirical studies, this thesis attempted to further explore the intercultural generalization of the benefits of parental AS. Study 1 relied on two cross-sectional databases collected from participants with a wide cultural variability. The aim was to explore the associations between CH, parental AS, and indicators of young individuals' psychosocial adjustment, and to examine whether CH plays a moderating role in the association between parental AS and young individuals' psychosocial adjustment. The results indicate that lower levels of CH among parents are associated with higher levels of AS. While parental AS is positively associated with well-being indicators (e.g., life satisfaction) and negatively associated with difficulties (e.g., symptoms), the results revealed no moderation by CH except for the relationship between parental AS and adolescents’ autonomous regulation. Study 2 utilized data from an experimental study measuring the effects of the parenting program How to talk so kids will listen & listen so kids will talk (Faber & Mazlish, 1980, 2000) to assess whether parents’ level of CH moderates the effects (or lack thereof) of the program on parenting and children’s mental health. Overall, the results suggest a generally undifferentiated impact on parenting and children’s mental health, even after conducting multiple tests (effects on AS, affiliation, and structure, as reported by parents and children, as well as children’s well-being and symptoms). The previously documented effects of the program generally do not differ based on parents’ ethnic identity. Among all the tests conducted, the only exception concerns AS as perceived by children. In summary, both studies focused on the potentially moderating role of CH in the relationship between autonomy-supportive parenting practices and various indicators of mental health in young individuals. Overall, the pattern of results suggests that youths whose parents promote their autonomy tend to exhibit better levels of psychosocial adjustment, regardless of the level of CH associated with their parents’ ethnicity. Furthermore, the results showed that the evaluated parental program has a similar impact on parenting and children’s mental health, regardless of the ethnicity of the participating parents. These findings generally support the position of SDT regarding the universal benefits of AS

Centrosome and retroviruses: The dangerous liaisons

Centrosomes are the major microtubule organizing structures in vertebrate cells. They localize in close proximity to the nucleus for the duration of interphase and play major roles in numerous cell functions. Consequently, any deficiency in centrosome function or number may lead to genetic instability. Several viruses including retroviruses such as, Foamy Virus, HIV-1, JSRV, M-PMV and HTLV-1 have been shown to hamper centrosome functions for their own profit, but the outcomes are very different. Foamy viruses, HIV-1, JSRV, M-PMV and HTLV-1 use the cellular machinery to traffic towards the centrosome during early and/or late stages of the infection. In addition HIV-1 Vpr protein alters the cell-cycle regulation by hijacking centrosome functions. Enthrallingly, HTLV-1 Tax expression also targets the functions of the centrosome, and this event is correlated with centrosome amplification, aneuploidy and transformation

Integrase and integration: biochemical activities of HIV-1 integrase

Integration of retroviral DNA is an obligatory step of retrovirus replication because proviral DNA is the template for productive infection. Integrase, a retroviral enzyme, catalyses integration. The process of integration can be divided into two sequential reactions. The first one, named 3'-processing, corresponds to a specific endonucleolytic reaction which prepares the viral DNA extremities to be competent for the subsequent covalent insertion, named strand transfer, into the host cell genome by a trans-esterification reaction. Recently, a novel specific activity of the full length integrase was reported, in vitro, by our group for two retroviral integrases (HIV-1 and PFV-1). This activity of internal cleavage occurs at a specific palindromic sequence mimicking the LTR-LTR junction described into the 2-LTR circles which are peculiar viral DNA forms found during viral infection. Moreover, recent studies demonstrated the existence of a weak palindromic consensus found at the integration sites. Taken together, these data underline the propensity of retroviral integrases for binding symmetrical sequences and give perspectives for targeting specific sequences used for gene therapy

A nuclear export signal within the structural Gag protein is required for prototype foamy virus replication

<p>Abstract</p> <p>Background</p> <p>The Gag polyproteins play distinct roles during the replication cycle of retroviruses, hijacking many cellular machineries to fulfill them. In the case of the prototype foamy virus (PFV), Gag structural proteins undergo transient nuclear trafficking after their synthesis, returning back to the cytoplasm for capsid assembly and virus egress. The functional role of this nuclear stage as well as the molecular mechanism(s) responsible for Gag nuclear export are not understood.</p> <p>Results</p> <p>We have identified a leptomycin B (LMB)-sensitive nuclear export sequence (NES) within the N-terminus of PFV Gag that is absolutely required for the completion of late stages of virus replication. Point mutations of conserved residues within this motif lead to nuclear redistribution of Gag, preventing subsequent virus egress. We have shown that a NES-defective PFV Gag acts as a dominant negative mutant by sequestrating its wild-type counterpart in the nucleus. Trans-complementation experiments with the heterologous NES of HIV-1 Rev allow the cytoplasmic redistribution of FV Gag, but fail to restore infectivity.</p> <p>Conclusions</p> <p>PFV Gag-Gag interactions are finely tuned in the cytoplasm to regulate their functions, capsid assembly, and virus release. In the nucleus, we have shown Gag-Gag interactions which could be involved in the nuclear export of Gag and viral RNA. We propose that nuclear export of unspliced and partially spliced PFV RNAs relies on two complementary mechanisms, which take place successively during the replication cycle.</p

Centrosomal pre-integration latency of HIV-1 in quiescent cells

Human immunodeficiency virus type 1 (HIV-1) efficiently replicates in dividing and non-dividing cells. However, HIV-1 infection is blocked at an early post-entry step in quiescent CD4+ T cells in vitro. The molecular basis of this restriction is still poorly understood. Here, we show that in quiescent cells, incoming HIV-1 sub-viral complexes concentrate and stably reside at the centrosome for several weeks. Upon cell activation, viral replication resumes leading to viral gene expression. Thus, HIV-1 can persist in quiescent cells as a stable, centrosome-associated, pre-integration intermediate

Tax ubiquitylation and SUMOylation control the dynamic shuttling of Tax and NEMO between Ubc9 nuclear bodies and the centrosome

International audiencen.

Centrosomal Latency of Incoming Foamy Viruses in Resting Cells

Completion of early stages of retrovirus infection depends on the cell cycle. While gammaretroviruses require mitosis for proviral integration, lentiviruses are able to replicate in post-mitotic non-dividing cells. Resting cells such as naive resting T lymphocytes from peripheral blood cannot be productively infected by retroviruses, including lentiviruses, but the molecular basis of this restriction remains poorly understood. We demonstrate that in G0 resting cells (primary fibroblasts or peripheral T cells), incoming foamy retroviruses accumulate in close proximity to the centrosome, where they lie as structured and assembled capsids for several weeks. Under these settings, virus uncoating is impaired, but upon cell stimulation, Gag proteolysis and capsid disassembly occur, which allows viral infection to proceed. The data imply that foamy virus uncoating is the rate-limiting step for productive infection of primary G0 cells. Incoming foamy retroviruses can stably persist at the centrosome, awaiting cell stimulation to initiate capsid cleavage, nuclear import, and viral gene expression

Characterization of Reemerging Chikungunya Virus

An unprecedented epidemic of chikungunya virus (CHIKV) infection recently started in countries of the Indian Ocean area, causing an acute and painful syndrome with strong fever, asthenia, skin rash, polyarthritis, and lethal cases of encephalitis. The basis for chikungunya disease and the tropism of CHIKV remain unknown. Here, we describe the replication characteristics of recent clinical CHIKV strains. Human epithelial and endothelial cells, primary fibroblasts and, to a lesser extent, monocyte-derived macrophages, were susceptible to infection and allowed viral production. In contrast, CHIKV did not replicate in lymphoid and monocytoid cell lines, primary lymphocytes and monocytes, or monocyte-derived dendritic cells. CHIKV replication was cytopathic and associated with an induction of apoptosis in infected cells. Chloroquine, bafilomycin-A1, and short hairpin RNAs against dynamin-2 inhibited viral production, indicating that viral entry occurs through pH-dependent endocytosis. CHIKV was highly sensitive to the antiviral activity of type I and II interferons. These results provide a general insight into the interaction between CHIKV and its mammalian host