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