CELL-SPECIFIC EXPRESSION OF MOUSE ALBUMIN PROMOTER - EVIDENCE FOR CELL-SPECIFIC DNA ELEMENTS WITHIN THE PROXIMAL PROMOTER REGION AND CIS-ACTING DNA ELEMENTS UPSTREAM OF -160

  • 5 June 1989
    • journal article
    • research article
    • Vol. 264  (16) , 9171-9179
Abstract
Regulation of albumin gene expression is believed to be mediated by multiple nuclear factors that interact with cis-acting DNA sequences within the frst 160 base pairs (bp) of the promoter. The minimal promoter sequences required to generate tissue-specific expression has not been clearly defined. We have constructed a series of transient expression vectors containing progressive deletions of the mouse albumin gene 5''-flanking sequences fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and include the Moloney murine leukemia viral (Mo-MuLV) enhancer. Promoter activity was determined in mouse hepatoma and fibroblast cell lines by chloramphenicol acetyltransferase and S1 nuclease analyses. All constructions were compared with -623 Albat-Mo-MuLV which contains all the sequences homology between the rat and mouse promoters. Low levels of expression were observed with -60 Albcat-Mo-MuLV (10%) in hepatoma but not fibroblasts cells. Addition of promoter sequence to -208 bp progressively increased activity to 190% in the hepatoma cells, while -308 and -1612 Albcat-Mo-MuLV had activity similar to the -623 Albact-Mo-MuLV level, and -3000 Albcat-Mo-MuLV showed a 2-fold reduction in transcriptional activity. The inclusion of promoter sequences upstream of -60 generated low levels of expression in the fibroblasts. We also show that factors from mouse liver nuclear extracts protect at least five regions of the albumin promoter upstream of -160. Our results indicate that tissue specificity is established within the proximal promoter region and that additional cis-acting elements that may have a functional role in the efficiency of albumin gene expression are located upstream of -160 bp.