Nobuyuki Kuramoto (#), Kiyokazu Ogita and Yukio Yoneda (*)
Department of Pharmacology, Setsunan University, Hirakata, Osaka 573-0101, Japan
(#) Mr. N. Kuramoto is a Research Fellow of the Japan Society for the Promotion of Science.
(*) To whom correspondence should be addressed at Department of Pharmacology, Kanazawa University Faculty of Pharmaceutical Sciences, Kanazawa, Ishikawa 920-0934, Japan.
Abstract: c-Myc family proteins, encoded by c-myc family proto-oncogenes, play critical roles in
mechanisms associated with proliferation, differentiation and apoptotic death in eukaryotic cells. These
functions are mediated by transcriptional activity of these proteins through binding to the E-box core
sequence CACGTG referred to as a Myc core element located at a promoter or enhancer region of the
individual target genes in the nucleus. Recent studies have demonstrated the presence of novel nuclear proteins that specifically recognize a Myc core element, in addition to c-Myc, Max, Mad and Mxi1. On the other
hand, a Myc core element has alternating purine/pyrimidine repeats which could undergo a conformational
transition from right-handed (B-DNA) to left-handed (Z-DNA) forms in the presence of a high concentration of salts such as Mg2+ and polyamines. Similarly, a Myc element has a homopurine-homopyrimidine
site that may take a triplex configuration in particular situations. We have searched for nuclear proteins that can
specifically recognize a Myc core element in different topological variations in murine brain.
Keywords: Transcription factor, c-Myc family protein, DNA binding, E-box element, DNA topology