Autoregulation of Oct-1 gene expression is mediated by two octa-sites in alternative promoter

Transcription of the oct-1 gene is regulated by two alternative promoters: U promoter and L promoter located upstream of the exons 1U and 1L, respectively. The L promoter contains two octamer sequences of opposite orientation: proximal (ATTTGCAT) and distal (ATGCAAAT), showing high affinity toward the Oct proteins. Binding of the Oct-1 protein to the octa-sites located in the L promoter region has been confirmed in footprinting experiments. Dual luciferase assay using wild-type and mutated promoters have indicated that mutations in the proximal octa-site resulted in significant transcription enhancement both in myeloma cell line NS/0 and in fibroblast cell line 3T3 (about twofold and fivefold, respectively), whereas mutations in the distal site decreased the promoter activity (about 10% and 40%, respectively). Mutations in both octa-sites enhanced the effect and increased transcription to about fourfold in myeloma cell line NS/0 and about sixfold in fibroblast cell line 3T3. These results demonstrate that transcription of the oct-1 gene may be autoregulated by two octa-sites within the L promoter. Different function and interactive tissue-specific effect of distal and proximal octamer sequences can be suggested.