It has now been more than two years since we said our last goodbye to Jan Svoboda (14 [...].

• MeSH
• lidé MeSH
• Retroviridae klasifikace   genetika   izolace a purifikace   fyziologie   MeSH
• retrovirové infekce virologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH
• úvodní články MeSH
• úvodníky MeSH

Individual groups of retroviruses and retroviral vectors differ in their integration site preference and interaction with the host genome. Hence, immediately after infection genome-wide distribution of integrated proviruses is non-random. During long-term in vitro or persistent in vivo infection, the genomic position and chromatin environment of the provirus affects its transcriptional activity. Thus, a selection of long-term stably expressed proviruses and elimination of proviruses, which have been gradually silenced by epigenetic mechanisms, helps in the identification of genomic compartments permissive for proviral transcription. We compare here the extent and time course of provirus silencing in single cell clones of the K562 human myeloid lymphoblastoma cell line that have been infected with retroviral reporter vectors derived from avian sarcoma/leukosis virus (ASLV), human immunodeficiency virus type 1 (HIV) and murine leukaemia virus (MLV). While MLV proviruses remain transcriptionally active, ASLV proviruses are prone to rapid silencing. The HIV provirus displays gradual silencing only after an extended time period in culture. The analysis of integration sites of long-term stably expressed proviruses shows a strong bias for some genomic features-especially integration close to the transcription start sites of active transcription units. Furthermore, complex analysis of histone modifications enriched at the site of integration points to the accumulation of proviruses of all three groups in gene regulatory segments, particularly close to the enhancer loci. We conclude that the proximity to active regulatory chromatin segments correlates with stable provirus expression in various retroviral species.

• Klíčová slova
• gene regulatory elements, genome-wide provirus distribution, provirus silencing, retrovirus integration,
• MeSH
• aktivace transkripce * MeSH
• Alpharetrovirus genetika   MeSH
• buněčné linie MeSH
• chromatin genetika   MeSH
• epigeneze genetická MeSH
• genetické vektory genetika   MeSH
• genový targeting MeSH
• HIV-1 genetika   MeSH
• integrace viru MeSH
• lidé MeSH
• myši MeSH
• plazmidy genetika   MeSH
• počátek transkripce MeSH
• proviry genetika   MeSH
• regulace exprese virových genů MeSH
• regulační oblasti nukleových kyselin * MeSH
• stabilita RNA MeSH
• umlčování genů MeSH
• virus myší leukemie genetika   MeSH
• zesilovače transkripce MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH

The extent of virus transmission among individuals and species is generally determined by the presence of specific membrane-embedded virus receptors required for virus entry. Interaction of the viral envelope glycoprotein (Env) with a specific cellular receptor is the first and crucial step in determining host specificity. Using a well-established retroviral model-avian Rous sarcoma virus (RSV)-we analyzed changes in an RSV variant that had repeatedly been able to infect rodents. By envelope gene (env) sequencing, we identified eight mutations that do not match the already described mutations influencing the host range. Two of these mutations-one at the beginning (D32G) of the surface Env subunit (SU) and the other at the end of the fusion peptide region (L378S)-were found to be of critical importance, ensuring transmission to rodent, human, and chicken cells lacking the appropriate receptor. Furthermore, we carried out assays to examine the virus entry mechanism and concluded that these two mutations cause conformational changes in the Env variant and that these changes lead to an activated, or primed, state of Env (normally induced after Env interaction with the receptor). In summary, our results indicate that retroviral host range extension is caused by spontaneous Env activation, which circumvents the need for original cell receptor. This activation is, in turn, caused by mutations in various env regions.

• Klíčová slova
• Rous sarcoma virus, envelope glycoprotein, receptor-independent entry, retrovirus, virus entry,
• MeSH
• genetické vektory * genetika   metabolismus   MeSH
• genové produkty env * genetika   metabolismus   MeSH
• krysa rodu Rattus MeSH
• kur domácí MeSH
• lidé MeSH
• missense mutace * MeSH
• nádorové buněčné linie MeSH
• substituce aminokyselin MeSH
• transdukce genetická * MeSH
• virus Rousova sarkomu * genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• genové produkty env * MeSH

This article summarizes the essential steps in understanding the chicken Rous sarcoma virus (RSV) genome association with a nonpermissive rodent host cell genome. This insight was made possible by in-depth study of RSV-transformed rat XC cells, which were called virogenic because they indefinitely carry virus genetic information in the absence of any infectious virus production. However, the virus was rescued by association of XC cells with chicken fibroblasts, allowing cell fusion between both partners. This and additional studies led to the interpretation that the RSV genome gets integrated into the host cell genome as a provirus. Study of additional rodent virogenic cell lines provided evidence that the transcript of oncogene v-src can be transmitted to other retroviruses and produce cell transformation by itself. As discussed in the text, two main questions related to nonpermissiveness to retrovirus infection remain to be solved. The first is changes in the retrovirus envelope gene allowing virus entry into a nonpermissive cell. The second is the nature of the permissive cell functions required by the nonpermissive cell to ensure infectious virus production. Both lines of investigation are being pursued.

• Klíčová slova
• cell transformation, nonpermissiveness to virus infection, virus integration, virus rescue,
• MeSH
• buněčné linie MeSH
• fúze buněk * MeSH
• genom virový genetika   MeSH
• genové produkty env genetika   MeSH
• krysa rodu Rattus MeSH
• kur domácí virologie   MeSH
• onkogenní protein pp60(v-src) genetika   MeSH
• proviry genetika   růst a vývoj   MeSH
• virová transformace buněk MeSH
• virus Rousova sarkomu genetika   růst a vývoj   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• genové produkty env MeSH
• onkogenní protein pp60(v-src) MeSH