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Self-Repairing Herpesvirus Saimiri Deletion Variants.

ABSTRACT: Herpesvirus saimiri (HVS) is discussed as a possible vector in gene therapy. In order to create a self-repairing HVS vector, the F plasmid vector moiety of the bacterial artificial chromosome (BAC) was transposed via Red recombination into the virus genes ORF22 or ORF29b, both important for virus replication. Repetitive sequences were additionally inserted, allowing the removal of the F-derived sequences from the viral DNA genome upon reconstitution in permissive epithelial cells. Moreover, these self-repair-enabled BACs were used to generate deletion variants of the transforming strain C488 in order to minimalize the virus genome. Using the en passant mutagenesis with two subsequent homologous recombination steps, the BAC was seamlessly manipulated. To ensure the replication capacity in permissive monkey cells, replication kinetics for all generated virus variants were documented. HVS variants with increased insert capacity reached the self-repair within two to three passages in permissive epithelial cells. The seamless deletion of ORFs 3/21, 12-14, 16 or 71 did not abolish replication competence. Apoptosis induction did not seem to be altered in human T cells transformed with deletion variants lacking ORF16 or ORF71. These virus variants form an important step towards creating a potential minimal virus vector for gene therapy, for example, in human T cells.

SUBMITTER: Heyn I

PROVIDER: S-EPMC9320899 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In latently infected marmoset T cells, Herpesvirus saimiri (HVS) expresses six microRNAs (known as miR-HSURs [H. saimiri U-rich RNAs]). The viral miR-HSURs are processed from chimeric primary transcripts, each containing a noncoding U-rich RNA (HSUR) and a pre-miRNA hairpin. To uncover the functions of miR-HSURs, we identified mRNA targets in infected cells using high-throughput sequencing of RNA isolated by cross-linking immunoprecipitation (HITS-CLIP). HITS-CLIP revealed hundreds of robust Argonaute (Ago) binding sites mediated by miR-HSURs that map to the host genome but few in the HVS genome. Gene ontology analysis showed that several pathways regulating the cell cycle are enriched among cellular targets of miR-HSURs. Interestingly, miR-HSUR4-3p represses expression of the p300 transcriptional coactivator by binding the open reading frame of its mRNA. miR-HSUR5-3p directly regulates BiP, an endoplasmic reticulum (ER)-localized chaperone facilitating maturation of major histocompatibility complex class I (MHC-I) and the antiviral response. miR-HSUR5-3p also robustly downregulates WEE1, a key negative regulator of cell cycle progression, leading to reduced phosphorylation of its substrate, cyclin-dependent kinase (Cdk1). Consistently, inhibition of miR-HSUR5-3p in HVS-infected cells decreases their proliferation. Together, our results shed light on the roles of viral miRNAs in cellular transformation and viral latency.Viruses express miRNAs during various stages of infection, suggesting that viral miRNAs play critical roles in the viral life cycle. Compared to protein-coding genes, the functions of viral miRNAs are not well understood. This is because it has been challenging to identify their mRNA targets. Here, we focused on the functions of the recently discovered HVS miRNAs, called miR-HSURs. HVS is an oncogenic gammaherpesvirus that causes acute T-cell lymphomas and leukemias in New World primates and transforms human T cells. A better understanding of HVS biology will help advance our knowledge of virus-induced oncogenesis. Because numerous cellular miRNAs play crucial roles in cancer, viral miRNAs from the highly oncogenic HVS might also be important for transformation. Here, we found that the miR-HSURs preferentially modulate expression of host cell cycle regulators, as well as antiviral response factors. Our work provides further insight into the functions of herpesviral miRNAs in virus-induced oncogenesis and latency.

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Self-Repairing Herpesvirus Saimiri Deletion Variants.

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