XRCC5 and HIV-1 infection: Finally, we performed chromatin immunoprecipitation (ChIP) analyses on T lymphoid lymphoma (SUP-T1) and leukemia (CEM-T4) cells - two cell lines physiologically more relevant for HIV-1 infection, but less easily transfectable with, and thus depletable of, Ku as compared to those used throughout this article - previously transduced for 48 h with HIV-1 NL4.3 env- aimed at assessing the binding of Ku80 to a site that includes a portion of the HIV-1 LTR (a part of the U3 region plus the complete R and U5 regions) and the leader region, which is located downstream of the LTR (Figure 5C).