Molecular characterization of full-length MLV-related endogenous retrovirus ChiRV1 from the chicken, Gallus gallus

We report the first full-length sequence of an endogenous retrovirus from the genome of domestic chicken, that is not related to the Avian leukemia viruses (ALV). This retrovirus, designated ChiRV1, clusters with Murine leukemia virus (MLV)-related retroviruses and hence is the first complete gammaretrovirus from the genome of a bird. Nevertheless it is not related to exogenous MLV-related retroviruses infecting chicken. The provirus is 9133 bp long and contains 90%-identical LTRs as well as reading frames for the gag, pol and env genes, interrupted by in-frame stop codons. Expression analysis showed that ChiRV1 is a transcribed provirus. Screening of the chicken genome database revealed 100 ChiRV1-related sequences that are grouped into three classes based upon LTR alignment and subsequent phylogenetic analysis.