ART-CH - A VL30 IN CHICKENS

The complete sequence of ART-CB, a recently found chicken retrotranspo son (A. V. Gudkov, E. A. Komarova, M. A. Nikiforov, and T. E. Zaitsevs kaya, J. Virol. 66:1726-1736, 1992), was characterized. ART-CH has the structure of a 3,300-bp-long provirus, including two 388-bp long term inal repeats (LTRs) (U3, 245 bp; R region, 17 bp; and U5, 126 bp), a t RNA(Trp)-binding site, and a polypurine tract, similar to avian leukos is viruses. At least some of the approximately 50 genomic copies of AR T-CH are transcribed into polyadenylated RNA, which is initiated and t erminated at the expected sites within the LTRs. In contrast to the re gulatory sequences involved in proviral expression and replication, th e internal regions of ART-CH seem to be completely defective. Several short regions of homology with avian leukosis virus genes, most of whi ch encode gag-related sequences, were found among different reading fr ames of ART-CH, which are not organized like regular retroviral genes. Both sequence analysis and restriction fragment length polymorphism a nalysis revealed a high degree of sequence (97% homology) and structur al similarity among members of the ART-CII family, indicating their co mmon origin and recent penetration into chicken DNA. ART-CK sequences were detected in mouse cells infected with Rous sarcoma virus produced by an ART-CH-expressing Rous sarcoma. These data are consistent with the hypothesis that ART-CH belongs to a class of defective retrotransp osons whose replication strategy requires the use of helper viruses. T hey might originate from an avian leukosis virus-related retrovirus wh ich completely lost its coding capacities as a result of multiple muta tions and deletions. These features apparently group ART-CH with the V L30 retrotransposons of rhodents.