ISOLATION OF THE HUMAN INTERLEUKIN-10 PROMOTER - CHARACTERIZATION OF THE PROMOTER ACTIVITY IN BURKITTS-LYMPHOMA CELL-LINES

Interleukin 10 (IL-10) is a pleiotropic growth and differentiation factor with potent suppressor functions on macrophages, T cells and NK cells and contributes to the regulation of proliferation and differentiation of B cells, The expression of IL-10 appears to be tightly regulated, as the levels of constitutive expression in normal cells is extremely low, In contrast to normal haematopoetic cells, Epstein-Barr virus (EBV)-immortalized B cells and EBV-positive Burkitt's lymphoma cells express high levels of IL-10 constitutively, In this report we have cloned and sequenced IL-10 promoter fragments and analysed their activity in EBV-positive Burkitt's lymphoma cells, A nested set of DNA fragments from the IL-10 gene 5'-flanking region was placed upstream of the luciferase gene and assayed for their ability to direct luciferase expression in Burkitt's lymphoma cells, We have identified elements within the 5'-flanking region of the human IL-10 gene which can activate or suppress the constitutive expression of IL-10. The essential promoter of the IL-10 gene, which induces low levels of luciferase expression, was found to require the major start site of transcription (+1), a TATA-box (-77) and up to 150 additional 5' nucleotides, Positive regulatory sequences are located between -1100/-900, Negative regulatory elements which abolish luciferase activity were identified between -8001-300.