Abstract

The avian nuclear protein, enhancer factor 1 (EF1), binds specifically to the long terminal repeat (LTR) of Rous sarcoma virus (RSV) in a region that has been implicated in enhancer/promoter function. We have characterized the in vitro binding properties of this factor from chick embryo nuclear extracts by methylation interference/protection footprinting of the wild-type LTR and also by gel electrophoretic mobility shift assays performed on a series of LTR mutants. We find that the inverted CCAAT pentanucleotide located at position −129 is essential for EF1 binding in vitro. Nucleotides flanking this element exert a smaller effect on binding. Linker-substitution and point mutations which reduce EF1 binding to this site in vitro also reduce promoter activity in transiently transfected cells. EF1 also binds with lower affinity to another inverted CCAAT box at position −65, an element which we show is also essential for transcriptional activity of the RSV LTR. We conclude, therefore, that EF1 is a CCAAT box-binding factor which is involved in the activation of RSV transcription in avian cells. Furthermore, we show that EF1 can recognize the CCAAT boxes of several other promoters in which the functional importance of this pentanucleotide has been established.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.