sentence: Mini-viral substrates for HIV-1 , BIV and EIAV INs were prepared by digestion of pU3U5 ( 51 ) , pBIV-U3U5 and pEIAV-U3U5 with ScaI , respectively.To obtain RU5 substrates for HIV-1 , BIV and EIAV INs , PCR fragments obtained using Taq DNA polymerase and T3P primer in combination with PC188 , PC139 , and PC169 , respectively , and pU3U5 , pBIV-U3U5 and pEIAV-U3U5 as templates , respectively , were digested with ScaI and the RU5-containing fragments were purified by electrophoresis through 2 % agarose gels .