Beyond blocking virus entry: Role of SERINC5 as a shield of genomic integrity

About This Grant

PROJECT SUMMARY/ABSTRACT Serine incorporator 5 (SERINC5) is a multipass transmembrane protein with potent antiviral activity. While its best-known role is inhibiting HIV-1 entry, recent findings from our lab revealed that SERINC5 also restricts expression from non-self-DNA, including HIV-1, adenoviruses, and plasmids, without affecting host genes. This unprecedented activity positions SERINC5 as a guardian of genomic integrity. However, this function also hinders gene therapy approaches that rely on viral vectors or plasmid DNA delivery. The long-term goal of this research is to modulate SERINC5 to exploit its non-self-DNA silencing activity in antiviral defense while bypassing it for gene therapy. Our central hypothesis is that SERINC5 tethers non-self-DNA, including the HIV- 1 pre-integration complex (PIC), to heterochromatin at the nuclear periphery, thereby limiting HIV-1 integration and restricting transcription from non-self-DNA. This hypothesis is based on our preliminary data showing that SERINC5 binds non-self-DNA, including HIV-1, and that it reduces its epigenetic deposition, which is consistent with non-self-DNA being trapped at heterochromatin regions. This hypothesis will be tested in two aims. Aim 1 will elucidate how SERINC5 reduces HIV-1 integration by examining the subnuclear localization of HIV-1 DNA, analyzing interactions of the PIC with host factors (CA–CPSF6, IN–LEDGF), and determining integration site selection. Aim 2 will define how SERINC5 restricts other forms of non-self-DNA by mapping functional motifs, testing its role as a DNA tether, assessing RNA pol-II coverage and epigenetic marks on the DNA of diverse DNA viruses, and identifying SERINC5-associated co-factors through comparative proteomic studies. Hits will be validated by gain and loss of function studies, which will be further confirmed in primary cells. This work is significant because it identifies a novel host mechanism that protects genomic integrity against invading DNA elements while providing the foundation to design strategies to overcome SERINC5 activity in therapeutic gene delivery. This research is conceptually innovative by revealing an unprecedented role of SERINC5 in the repression of non-self-DNA. The proposed studies will advance our understanding of intrinsic immunity and inform the design of antiviral strategies and improved gene therapy methods.