A chimeric construct (VCD) consisting of parts from viral jun, chicken c-jun, and chicken junD was cloned into the replication-competent retroviral RCAS vector. This construct, RCAS-VCD, was found to have a higher focus forming potential in quail fibroblasts than the equivalent construct RCAS-VJ-1, expressing viral jun. DNAs from RCAS-VCD and RCAS-VJ-1 were transfected into primary quail embryo fibroblasts. Cells derived from one RCAS-VCD-induced focus survived cell crisis, which became manifest after 15 passages, and could be expanded into a long-term culture. This cell line, termed VCD, has been passaged for over 100 times so far. The cells grow to very high densities and then pile up into clumps of rounded cells. The culture releases a transforming virus with a titer of 10(5) FFU/ml, as tested on primary quail embryo fibroblasts. The transformed phenotype of VCD cells was verified by agar colony formation. VCD cells are capable of anchorage-independent growth with a cloning efficiency of 10%. Southern blot analysis of genomic DNA from VCD cells showed proviral integration of the RCAS construct without detectable rearrangements. Northern and Western blot analyses confirmed correct expression from integrated RCAS-VCD of predicted RNAs and of the chimeric Jun(VCD) protein. jun(VCD)-transformed cells provide a constant source of homogeneous cellular material for the investigation of the molecular mechanisms of jun-induced cell transformation and for the identification of direct and indirect targets of Jun protein function.