Recently, Molecular Biology and Evolution (impact factor: 11.062), a famous international evolutionary biology journal, published the latest research on retrovirus gene co-option by Professor Guanzhu Han's research group from the School of Life Sciences under the title "Frequent retroviral gene co-option during the evolution of vertebrates".
Retroviruses need to be integrated into the host genome to complete their replication. When a retrovirus infects the germ cells of host, the integrated retrovirus will pass from parent to offspring, thus forming an endogenous retrovirus. Endogenous retroviruses are widely distributed in vertebrate genes. The vast majority of endogenous retroviruses accumulate various mutations and become inactivated or fragmented in the host genome. Hosts sometimes use endogenous retroviral genes to perform their biological functions (Fig. 1), a process known as co-option in evolutionary biology. For example, Fv1, a limiting factor that inhibits multiple retroviral replication, and syncytins, which is involved in embryonic development, are co-opted retroviral genes. However, there has been no systematic study on retroviral gene co-option in vertebrates.
A total of 177 retrovirus co-option events were found in the genome of 756 vertebrates (Fig. 2). Among them, 93 co-option events were related to the retrovirus gag gene, which mainly occurred in mammals and birds. There were 84 co-option events related to the retrovirus env gene and the env gene co-option events mainly occurred in mammals, birds and fish. By analyzing the time of co-option events, it was found that the number of co-option events increased with the passage of time, and only a few co-opted retroviral genes were maintained on a long timescale. These results indicate that retroviral gene co-option can occur and be lost frequently in vertebrates.
It is generally believed that host genes involved in the evolutionary arms race between virus and host will be positively selected. In this study, evidence of positive selection among many co-opted retroviral genes through selection pressure analysis were found, suggesting that these genes may participate in the evolutionary arms race between virus and host. In addition, the evolution of some co-opted retroviral genes was mainly negative selection, indicating that these genes may be mainly involved in non-antiviral host functions. The co-opted retroviral genes were subjected to different selection pressures, indicating that these co-opted retroviral genes may perform a variety of host cell biological functions. In conclusion, this study provides a panoramic view of retrovirus co-option events in the evolution of vertebrates and is of great significance for a comprehensive understanding of the evolution of the interaction between retroviruses and vertebrates.
This research has been published in Molecular biology and Evolution (https://doi.org/10.1093/molbev/msaa180) with graduate student Jianhua Wang as the first author and Professor Guanzhu Han as the corresponding author. This research is supported by the National Natural Science Foundation of China and the Priority Academic Program Development of Jiangsu Higher Education Institutions of Jiangsu Province.