Nucleic Acids Research, 1990, Vol. 18, No. 15 4513-4521
© 1990
MOLECULAR BIOLOGY |
A novel transcriptional activator (PO-B) binds between the TATA box and cap site of the pro-opiomelanocortin gene
Hormone Action and Oncogenesis Section, Laboratory of Experimental Carcinogenesis Bethesda, MD 20892, USA
*To whom correspondence should be addressed
Received April 4, 1990. Revised June 26, 1990. Accepted June 26, 1990.
We demonstrate that a factor (PO-B), detected in a number of mammalian cell lines, binds specifically between the TATA box and the transcription initiation site of the pituitary-specific pro-opiomelanocortin (POMC) gene. Methylation interference and DNAse 1 footprint analysis revealed that the binding site of this protein, – 3 to –15, does not overlap the POMC TATA box or cap site. Mutation of the PO-B binding site significantly decreased the transcriptional activity of the POMC promoter after transient transfection into the ATt-20 mouse pituitary tumor cell line and also in in vitro transcription assays. In contrast, mutation of the TATA box produced no overall decrease in transcription in vivo but induced multiple heterogenous start sites in vitro. A vector harboring the PO-B site alone was unable to direct transcription initiation. POB represents a new transcription factor that may be able to facilitate POMC gene expression by interacting with components of the transcription initiation complex.
+Present address: Department of Pharmacology, Georgetown University, Washington DC 20007, USA
1laboratory of Molecular Virology, National Cancer Institute, Bethesda, MD 20892, USA