Understanding how SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) efficiently reproduces itself by taking resources from the human host could facilitate the development of drugs against the virus. SARS-CoV-2 translates its own proteins by using the host tRNAs, so that its GC or codon usage should fit that of the host cells. It is necessary to study both the virus and human genomes in the light of evolution and adaptation. The SARS-CoV-2 virus has significantly lower GC content and GC3 as compared to human. However, when we selected a set of human genes that have similar GC properties to SARS-CoV-2, we found that these genes were enriched in particular pathways. Moreover, these human genes have the codon composition perfectly correlated with the SARS-CoV-2, and were extraordinarily highly expressed in human lung tissues, demonstrating that the SARS-CoV-2 genes have similar GC usage as compared to the lung expressed human genes. RSCU (relative synonymous codon usage) and CAI (codon adaptation index) profiles further support the matching between SARS-CoV-2 and lungs. Our study indicates that SARS-CoV-2 might have adapted to the human lung environment by observing the high correlation between GC usage of SARS-CoV-2 and human lung genes, which suggests the GC content of SARS-CoV-2 is optimized to take advantage of human lung tissues.

了解 SARS-CoV-2（严重急性呼吸系统综合症冠状病毒 2）如何通过从人类宿主获取资源来有效地自我复制，可以促进针对该病毒的药物的开发。 SARS-CoV-2 使用宿主 tRNA 翻译自己的蛋白质，因此其 GC 或密码子使用应适合宿主细胞的使用。有必要从进化和适应的角度研究病毒和人类基因组。与人类相比，SARS-CoV-2 病毒的 GC 含量和 GC3 显着降低。然而，当我们选择一组与 SARS-CoV-2 具有相似 GC 特性的人类基因时，我们发现这些基因在特定途径中富集。此外，这些人类基因的密码子组成与 SARS-CoV-2 完全相关，并且在人类肺组织中表达异常高，这表明 SARS-CoV-2 基因与肺表达的人类基因相比具有相似的 GC 使用情况。 RSCU（相对同义密码子使用）和 CAI（密码子适应指数）图谱进一步支持 SARS-CoV-2 与肺部之间的匹配。我们的研究表明，通过观察 SARS-CoV-2 的 GC 使用与人类肺部基因之间的高度相关性，SARS-CoV-2 可能已经适应了人类肺部环境，这表明 SARS-CoV-2 的 GC 含量被优化为利用人体肺组织。