A novel snail-related transcription factor Smuc regulates basic helix-loop-helix transcription factor activities via specific E-box motifs.
Snail family proteins are zinc finger transcriptional regulators first identified in Drosophila which play critical roles in cell fate determination. We identified a novel Snail -related gene from murine skeletalmusclecells designated Smuc. Northern blot analysis showed that Smuc was highly expressed in skeletal muscle and thymus. Smuc contains five putative DNA-binding zinc finger domains in its C-terminal half. In electrophoretic mobility shift assays, recombinant zinc finger domains of Smuc specifically bound to CAGGTG and CACCTG E-box motifs (CANNTG). Because basic helix-loop-helix transcription factors (bHLH) bind to the same E-box sequences, we examined whether Smuc competes with the myogenic bHLH factor MyoD for DNA binding. Smuc inhibited the binding of a MyoD-E12 complex to the CACCTG E-box sequence in a dose-dependent manner and suppressed the transcriptional activity of MyoD-E12. When heterologously targeted to the thymidine kinase promoter as fusion proteins with the GAL4 DNA-binding domain, the non-zinc finger domain of Smuc acted as a transcriptional repressor. Furthermore, overexpression of Smuc in myoblasts repressed transactivation of muscle differentiation marker Troponin T. Thus, Smuc might regulate bHLH transcription factors by zinc finger domains competing for E-box binding, and non-zinc finger repressor domains might also confer transcriptional repression to control differentiation processes.
Kataoka
H
H
Department of Geriatric Medicine, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
Murayama
T
T
Yokode
M
M
Mori
S
S
Sano
H
H
Ozaki
H
H
Yokota
Y
Y
Nishikawa
S
S
Kita
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D017931:DNA Primers; D018257:Helix-Loop-Helix Motifs; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D017570:MyoD Protein / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020107:Troponin T / Q000378:metabolism
D017931:DNA Primers; D017570:MyoD Protein; D012333:RNA, Messenger; C404767:Snai3 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D020107:Troponin T; D004247:DNA