RETROVIRAL SEQUENCE LOCATED IN BORDER REGION OF SHORT UNIQUE REGION AND SHORT TERMINAL REPEAT OF MD5 STRAIN OF MAREKS-DISEASE VIRUS TYPE-1

A 246-base pair (bp) retroviral sequence, which was homologous to a lo ng terminal repeat of avian erythroblastosis virus (AEV), was detected and cloned from Md5 strain (Md5) of Marek's disease virus type 1 (MDV 1) by representational difference analysis (RDA). The retroviral seque nce was thought to be located in the border region of short unique reg ion (U-s) and short terminal repeat (TRs), but did not exist in the bo rder region of Us and the inverted short repeat (IRs) of the Md5 genom e. A cloned fragment of the US/TRs border region of the Md5 genome sho wed a construction of U-E'-R-U'-E-TRs with the regions designated as f ollows: E, expanded TRs reported by Jones et al. [Proc. Natl. Acad. Sc i. U.S.A. 90, 3855, 1993]; E', a partial copy of the expanded TRs; R, the retroviral sequence detected in Md5 genome; U, TRs-end sequence of U-s; U', a partial copy of TRs-end sequence of U-s. The sequence unit indicated as E'-R-U' was thought to be heterogeneously repeated in th e Md5 genome. Since this retroviral sequence reportedly did not exist in the original stock of Md5, the retroviral sequence is thought to be inserted in the Md5 genome without experimental co-infection of avian cells with retrovirus and MDV1. These results suggest that RDA could be useful for the detection of retroviral sequences in the herpesvirus genome.