Preliminary characterization of a nuclear factor interacting with the silencer element at the 3'-side of the chicken...

A silencer element has been identified previously on the 3'-side of the chicken alpha-globin genes placed next to the major enhancer in this domain (Recillas Targa et al., unpublished). Deletion fragments of this negative element show the requirement of the entire DNA segment for maximum silencing activity. Additionally, the sub-fragments including the previously defined SF1 (Silencer Factor 1) sequence seem to play an important role on the negative action of this silencer. Preliminary characterization of the nuclear factor interacting with the SF1 sequence was carried out. Methylation interference experiments show the contact points and, by electrophoretic retardation analysis with SF1 and SF1-mutated oligonucleotides, the critical role of these contacts points on the formation of the DNA-protein complex could be demonstrated. These results provide a basis for further experiments on the characterization and understanding of the mechanisms of action of the coupled positive and negative regulatory elements.