Antiretroviral activity of ancestral TRIM5α

The antiretroviral protein TRIM5 alpha is known to have evolved different restriction capacities against various retroviruses, driven by positive Darwinian selection. However, how these different specificities have evolved in the primate lineages is not fully understood. Here we used ancestral protein resurrection to estimate the evolution of antiviral restriction specificities of TRIM5 alpha on the primate lineage leading to humans. We used TRIM5 alpha coding sequences from 24 primates for the reconstruction of ancestral TRIM5 alpha sequences using maximum-likelihood and Bayesian approaches. Ancestral sequences were transduced into HeLa and CRFK cells. Stable cell lines were generated and used to test restriction of a panel of extant retroviruses (human immunodeficiency virus type 1 [HIV-1] and HIV-2, simian immunodeficiency virus [SIV] variants SIVmac and SIVagm, and murine leukemia virus [MLV] variants N-MLV and B-MLV). The resurrected TRIM5 alpha variant from the common ancestor of Old World primates (Old World monkeys and apes, similar to 25 million years before present) was effective against present day HIV-1. In contrast to the HIV-1 restriction pattern, we show that the restriction efficacy against other retroviruses, such as a murine oncoretrovirus (N-MLV), is higher for more recent resurrected hominoid variants. Ancestral TRIM5 alpha variants have generally limited efficacy against HIV-2, SIVagm and SIVmac. Our study sheds new light on the evolution of the intrinsic antiviral defense machinery and illustrates the utility of functional evolutionary reconstruction for characterizing recently emerged protein differences.