The SV40 enhancer can be dissected into multiple segments, each with a different cell type specificity

The SV40 enhancer is known to be active in a wide variety of tissues and species. It contains a number of sequence motifs that can be bound by protein factors and whose integrity is essential for full enhancer activity. We have individually analyzed three synthetic oligonucleotides derived from sequences present within the SV40 enhancer: two oligonucleotides contain variants of the enhancer "core" sequence (designated corePVUII and coreC) and the third represents a region containing a decanucleotide homology to the immunoglobulin promoters/enhancers (designated SPHI). The oligonucleotides were multimerized and linked to a beta-globin test gene. Transcripts of the test gene were analyzed following transient expression in 10 cell lines representing a broad spectrum of tissues. We show that each of the three short segments can individually act as an enhancer when present in multiple copies. None of these enhancers is ubiquitously active; however, each shows activity in a distinctive subpopulation of cell lines. This cell type specificity is most remarkable in the case of the two oligonucleotide segments containing the core sequences. One of these is primarily active in CV-1 cells, whereas the other exhibits a cell type specificity identical to that of the entire enhancer, possibly identifying it as the most important sequence element within the native SV40 enhancer. Our data suggest that a particular cell type specificity is typical for individual enhancer segments, and that enhancers of differing specificity can be assembled from the individual sequence motifs by combining them in different patterns.