The basic helix-loop-helix transcription factors dHAND and eHAND exhibit dimerization characteristics that suggest complex regulation of function*

Beth A. Firulli, Daniel B. Hadzic, Jennifer R. McDaid, Anthony Firulli

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

dHAND and eHAND are basic helix-loop-helix (bHLH) transcription factors expressed during embryogenesis and are required for the proper development of cardiac and extraembryonic tissues. HAND genes, like the myogenic bHLH genes, are classified as class B bHLH genes, which are expressed in a tissue-restricted pattern and function by forming heterodimers with class A bHLH proteins. Myogenic bHLH genes are shown not to form homodimers efficiently, suggesting that their activity is dependent on their E-protein partners. To identify HIPs (HAND-interacting proteins) that regulate the activity of the HAND genes, we screened an 9.5-10.5-day-old mouse embryonic yeast two-hybrid library with eHAND. Several HIPs held high sequence identity to eHAND, indicating that eHAND could form and function as a homodimer. Based on the high degree of amino acid identity between eHAND and dHAND, it is possible that dHAND could also form homodimers and heterodimers with eHAND. We show using yeast and mammalian two-hybrid assays as well as biochemical pull-down assays that eHAND and dHAND are capable of forming both HAND homo- and heterodimers in vivo. To investigate whether HAND genes form heterodimers with other biologically relevant bHLH proteins, we tested and show HAND heterodimerization with the recently identified Hairy-related transcription factors, HRT1-3. This finding is exciting, because both HRT and HAND genes are coexpressed in the developing heart and limb and both have been implicated in establishing tissue boundaries and pattern formation. Moreover, competition gel shift analysis demonstrates that dHAND and eHAND can negatively regulate the DNA binding of MyoD/E12 heterodimers in a manner similar to MISTI and Id proteins, suggesting a possible transcriptional inhibitory role for HAND genes. Taken together, these results show that dHAND and eHAND can form homo- and heterodimer combinations with multiple bHLH partners and that this broad dimerization profile reflects the mechanisms by which HAND genes regulate transcription.

Original languageEnglish (US)
Pages (from-to)33567-33573
Number of pages7
JournalJournal of Biological Chemistry
Volume275
Issue number43
DOIs
StatePublished - Oct 27 2000
Externally publishedYes

Fingerprint

Basic Helix-Loop-Helix Transcription Factors
Dimerization
Genes
Proteins
Tissue
Yeast
Assays
Transcription Factor 3
Two-Hybrid System Techniques
Electrophoretic Mobility Shift Assay
Transcription
Libraries
Embryonic Development
Transcription Factors
Extremities
Yeasts
Gels
Amino Acids

ASJC Scopus subject areas

  • Biochemistry

Cite this

The basic helix-loop-helix transcription factors dHAND and eHAND exhibit dimerization characteristics that suggest complex regulation of function*. / Firulli, Beth A.; Hadzic, Daniel B.; McDaid, Jennifer R.; Firulli, Anthony.

In: Journal of Biological Chemistry, Vol. 275, No. 43, 27.10.2000, p. 33567-33573.

Research output: Contribution to journalArticle

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