Long Terminal Repeats (LTRs) are part of the genome of retroviruses, located at both ends of the viral DNA. They consist of three regions: U3, R, and U5, which are involved in the transcriptional regulation and integration of the virus. The localization of LTRs in host cells depends on the integration site of the virus and can affect the expression of viral genes and the production of viral particles. By interacting with host cell transcription factors, LTRs participate in activating viral gene transcription and regulating the signal pathways of viral replication. The sequence and structure of LTRs vary in different viruses, and their specific expression and mutations are closely related to the pathogenicity, drug resistance, and host adaptation of the virus.