SEQUENCE-ANALYSIS OF MUS DUNNI ENDOGENOUS VIRUS REVEALS A HYBRID VL30GIBBON APE LEUKEMIA VIRUS-LIKE STRUCTURE AND A DISTINCT ENVELOPE/

Mus dunni endogenous virus (MDEV) can be activated from M, dunni cells by exposing the cells to hydrocortisone or 5-iodo-2'-deoxyuridine. In terference analysis has revealed that MDEV uses a receptor for cell en try that is different from those used by other murine retroviruses. Th e entire genome has now been sequenced, revealing a long terminal repe at (LTR)-gag-poLenv-LTR structure typical of simple retroviruses of th e murine leukemia virus genus, with no additional open reading frames between env and the 3' LTR, The LTRs and other noncoding regions of MD EV are most closely related to those of VL30 elements, while the major ity of the coding sequences are most closely related to those of gibbo n ape leukemia virus. MDEV represents the first example of a naturally occurring, replication-competent virus with sequences closely related to VL30 elements. The U3 region of MDEV contains six nearly perfect 8 0-bp repeats and the beginning of a seventh, and the region expected t o contain the packaging sequence contains approximately four imperfect 33-bp repeats. The receptor specificity domains of the envelope are u nique among retroviruses and show no apparent similarity to regions of known proteins.