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Mol. Cell. Biol., 07 1995, 3813-3822, Vol 15, No. 7
SM Hollenberg, R Sternglanz, PF Cheng and H Weintraub
With modified two-hybrid technology, we have isolated a member of a new
family of basic helix-loop-helix (bHLH) transcription factors. Thing1 (Th1)
was identified in a screen of a mouse embryo cDNA library as a partner for
the Drosophila E protein daughterless. RNA in situ hybridization and
reverse transcriptase-PCR demonstrate a stage- and tissue-specific
distribution for the expression of Th1. Although tissue specific, the
expression pattern of Th1 is fairly complex. During development, Th1 mRNA
is widely expressed in extraembryonic tissues, portions of the heart,
autonomic ganglia, the gut, and pharyngeal arches. At embryonic day 7.5
(E7.5), extraembryonic derivatives show robust Th1 expression. By E8.5,
expression in the embryonic heart becomes detectable. During the next 2
days of development, the signal also includes gut and pharyngeal arches.
Predominant expression at E13.5 is in neural crest derivatives, especially
the autonomic nervous system and adrenal medulla. Expression of Th1
persists in the adult, in which it is localized to the smooth muscle cells
of the gut. In vitro, Th1 protein recognizes a set of DNA sites that are
more degenerate than has been determined for other bHLH factors, indicating
a reduced binding specificity. Transient transfection of NIH 3T3 cells with
GAL4- Th1 fusions reveals a repression activity mediated by the Th1 bHLH
domain. In combination, these properties define Th1 as a new bHLH protein
with a unique set of properties.
Copyright © 1995, American Society for Microbiology
Identification of a new family of tissue-specific basic helix-loop- helix proteins with a two-hybrid system
Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
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