Cell-line specific transcription rates of the RET gene and functional domains in its minimal promoter

To gain insight into the RET gene transcriptional regulation we analysed its mRNA expression, transcription rate, and promoter activity in different cell lines, showing that RET transcription is highly cell-line specific. By using a panel of promoter deletion constructs in transient transfection assays we identified the −147/+53 fragment as the main functional element. GMSA experiments indicated binding by Sp1 and a CACCC binding protein to multiple sites within the promoter. Upon deletion analysis Sp1 appeared to be the main positive regulator of promoter activity. The −147/+53 sequence did not reproduce the cell-line specific activity of the endogenous gene in vitro, raising the question of how the regulated pattern of RET transcription is achieved at the molecular level. To address this topic, both the search for far-sited tissue-specific enhancers/silencers and the study of chromatin structure within the RET locus should be envisaged.