The murine lymphotoxin gene promoter. Characterization and negative regulation
Fashena, S.J.; Tang, W.L.; Sarr, T.; Ruddle, N.H.
Journal of Immunology 145(1): 177-183
1990
ISSN/ISBN: 0022-1767 PMID: 2358671 Document Number: 347861
Murine lymphotoxin (LT; TNF-.beta.) gene upstream regulatory elements were identified by linking fragments of 5' DNA to the chloramphenicol acetyl transferase gene. Fragment LT1 (-293 to +77 in relation to the proximal cap site) exhibited promoter activity which drove CAT expression in transfected murine fibroblasts and T lymphomas. Primer extension analysis of endogenous LT message confirmed that LT1 contained the necessary elements required for promoter function. Promoter activity was not observed when LT2 (-662 to +77), LT3 (-1186 to +77), or LT3.delta.AX (-1186 to +77 (.DELTA.-662/-269)) were ligated to the chloramphenicol acetyl transferase gene and transfected into fibroblasts or T lymphomas. At least one upstream repressor element is postulated to account for this promoter inhibition. In contrast to the results obtained with fibroblast and T cell transfectants, LT1 was inactive in the B cell transfectants A20 and P3X63. This suggests that some B cells express a repressor factor that inhibits that LT promoter and/or they lack the necessary positive regulatory factors.