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Project A3: Justine Lagisquet, doctoral researcher (PhD)

Assessing the impact of TRIM5α polymorphisms on LINE-1 retroelements restriction

LINE-1 retroelements are mobile genetic elements that contribute to the diversity of the human genome. However, uncontrolled retrotransposition events can have adverse effects and cause various genetic disorders. Therefore, hosts have evolved mechanisms to hold these elements at bay and maintain genome integrity. One of these mechanisms in humans is the retroviral restriction factor TRIM5α, which senses and restricts the replication of LINE-1 elements, thereby underlining its role as a guardian of the human genome. Episodes of positive selection, preceding the appearance of lentiviruses, like HIV-1, suggest that older threats such as simple retroviruses or endogenous retroelements might play a role in TRIM5 evolution. Interestingly, various single nucleotide polymorphisms (SNPs) of TRIM5α are present in the human population. Some of these alleles were shown to be defective against retroviruses, which raised questions whether their activity against endogenous genetic elements may influence their persistence in the human population. Thus, we aim to determine whether LINE-1 retrotranposition is targeted differently by the most frequent TRIM5α SNPs present within the human population. An initial retrotransposition assay revealed that the frequent TRIM5α SNP, H43Y, efficiently counteracts LINE-1 replication. Therefore, the activity of TRIM5α H43Y against LINE-1 retroelements will be further analyzed. In addition, the effect of the H43Y variant on retroviral restriction and on TRIM5α structure will also be assessed. Since the E3-ubiquitin ligase activity of TRIM5α H43Y has been suggested to be altered, its ability to induce innate signaling pathways in response to LINE-1 elements will be determined. Finally, the contribution of the signaling pathways to TRIM5α H43Y-mediated LINE-1 restriction will be evaluated. Together, this study will strengthen the role of TRIM5α as pattern recognition receptor sensing LINE-1 retroelements and gain further insights into the persistence of frequent SNPs of the restriction factor TRIM5α in the human population.