Ribosomal protein (Rp) L6 is also defined as Taxreb107 (Tax responsive element binding protein 107) for its binding activity to the long terminal repeats of human T cell leukemia virus (HTLV)-I. We cloned the genomic gene of mouse RpL6/Taxreb107 and analyzed its exon/intron structures. The promoter of RpL6/Taxreb107 contains recognition sites for multiple transcription factors including nuclear factor (NF)-kappa B. Luciferase reporter assay showed that the RpL6/Taxreb107 promoter has a constitutive activity in transfected cells, and the constitutive activity depends on the intact promoter. Expression of HTLV-I viral protein Tax mildly but reproducibly induced RpL6/Taxreb107 mRNA and promoter activity. We provide evidence suggesting that induction of RpL6/Taxreb107 by Tax is at least partially mediated by the NF-kappa B site in the promoter of RpL6/Taxreb107. Taken together, Tax up-regulates RpL6/Taxreb107 and this may provide a feedback mechanism to facilitate proliferation of HTLV-I-infected cells and production of viral particles.