Cloning of mouse genomic ribosomal protein L6 gene and analysis of its promoter.

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)-κB. 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-κB 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.