Host Factors in Retroviral Integration and the Selection of Integration Target Sites

Abstract

In order to replicate, a retrovirus must integrate a DNA copy of the viral RNA genome into a chromosome of the host cell. The study of retroviral integration has advanced considerably in the last few years. Here we focus on host factor interactions and the linked area of integration targeting. Genome-wide screens for cellular factors affecting HIV replication have identified a series of host cell proteins that may mediate subcellular trafficking of integration complexes, nuclear import, and integration target site selection. The cell transcriptional co-activator protein LEDGF/p75 has been identified as a tethering factor important for HIV integration, and recently, BET proteins (Brd2, 4, and 4) have been identified as tethering factors for the gammaretroviruses. A new class of HIV inhibitors has been developed targeting the HIV-1 IN-LEDGF binding site, though surprisingly these inhibitors appear to block assembly late during replication and do not act at the integration step. Going forward, genome-wide studies of HIV-host interactions offer many new starting points to investigate HIV replication and identify potential new inhibitor targets.

A supramolecular assembly mediates lentiviral DNA integration

“…S3). As expected for a lentivirus (9), MVV displayed a strong preference for transcription units, with 70.2% of integration sites found within predicted sheep genes, compared with 43.7% in the in vitro generated sample (P < 10 −150 ).…”

“…3B), which was recently implicated in noncatalytic interactions with nucleosomal DNA in the PFV system (24). Lentiviral integration is exquisitely selective toward highly active and gene-rich genomic loci, a property that is explained, at least in part, by the direct interaction between IN and chromatinassociated LEDGF (9). The MVV intasome structure is compatible with binding as many as 16 molecules of the host factor (fig.…”

Programming CAR T Cell Tumor Recognition: Tuned Antigen Sensing and Logic Gating

“…After chromosomal integration, CAR expression is driven by the 5′ long terminal repeat in γ-retroviral vectors or by an exogenous promoter, usually long EF1α, in lentiviral vectors. Although CAR expression is variegated in T cells due to the semirandom integration pattern ( 104 ), CAR T cells have shown remarkable therapeutic activity against hematologic malignancies using either γ-retroviral or lentiviral vectors ( Table 1 ). Nonviral approaches have also been used to generate clinical-grade CAR T cells, primarily utilizing the Sleeping Beauty or piggyBac transposons ( 105, 106 ).…”

Transposon vector-mediated stable gene transfer for the accelerated establishment of recombinant mammalian cell pools allowing for high-yield production of biologics

“…The generation of polyclonal pools of genetically modified mammalian cells for the purpose of recombinant protein production was first demonstrated using MLV and HIV-1 vectors mediating gene transduction (Oberbek et al 2011;Stitz 2011;Elegheert et al 2018). These approaches capitalized on the stable integration of multiple vector copies per cell and the sustained expression of the transgenes as a result of the favored insertion sites located in the proximity of transcriptional start sites and active cellular transcription units (Craigie and Bushman 2014;Gogol-Döring et al 2016). The productivity of the recombinant cell pools and cell clones established upon viral vectormediated gene transduction was remarkable.…”