Author(s): Reinhold W, Emens L, Itkes A, Blake M, Ichinose I,
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Abstract We demonstrated that MIF-1, identified initially as a binding activity that associated with the intron I element of the c-myc gene, consists of two polypeptides, the myc intron-binding peptide (MIBP1) and the major histocompatibility class II promoter-binding protein, RFX1. Using a polyclonal antiserum directed against either oligonucleotide affinity-purified MIBP1 or a peptide derived from RFX1, we showed that MIBP1 and RFX1 are distinct molecules that associate in vivo and are both present in DNA-protein complexes at the c-myc (MIF-1) and major histocompatibility complex class II (RFX1) binding sites. We have also found that MIBP1 and RFX1 bind to a regulatory site (termed EP) required for enhancer activity of hepatitis B virus. In addition, we have identified MIF-1-like sequences within regulatory regions of several other viral genes and have shown that MIBP1 binds to these sites in cytomegalovirus, Epstein-Barr virus, and polyomavirus. We have also demonstrated that the MIF-1 and EP elements can function as silencers in the hepatocarcinoma HepG2 and the cervical carcinoma HeLa cell lines. These findings indicate that MIBP1 and EP/RFX1 can associate in vivo and may regulate the expression of several distinct cellular and viral genes.
This article was published in Mol Cell Biol
and referenced in Journal of Cytology & Histology