Cryptic enhancer elements in luciferase reporter vectors respond to the osteoblast-specific transcription factor Osf2/Cbfa1

Luciferase reporter vectors are commonly used for the functional analysis o f basal promoter and enhancer elements of eukaryotic genes. Randomly occurr ing cis-acting elements in the vector sequences that can spuriously respond to various transcription factors, combined with the high sensitivity of th e luciferase assay system, could make these vectors unsuitable for function al studies with certain transcription factors. Here, we provide evidence th at pGL2-Basic and pGL3-Basic are transactivated by the osteoblast-specific transcription factor Cbfa1 and estrogen receptor alpha probably through ran domly occurring cis-acting elements in the vector sequences. Our results hi ghlight the limitations of pGL2-Basic and pGL3-Basic vectors in promoter tr ansactivation/repression studies. The results also emphasize the need to pe rform appropriate controls and test the expression levels with a particular transcription factor and promoterless luciferase reporter vector combinati on.