Send to

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 1997 Sep 19;272(38):23930-7.

Basic helix-loop-helix protein sequences determining differential inhibition by calmodulin and S-100 proteins.

Author information

Division of Tumour Biology, Department of Applied Cell and Molecular Biology, Umeâ University, S-901 87 Umeâ, Sweden.


Basic helix-loop-helix (bHLH) proteins are a group of transcription factors that are involved in differentiation and numerous other cellular processes. The proteins include the widely expressed class A bHLH proteins (E proteins) and the tissue-specific class B proteins. Previous studies have shown that calmodulin can inhibit the DNA binding activity of certain E proteins but not their heterodimers with class B proteins. Here we show that calmodulin binds to the DNA-interacting basic sequence within the bHLH domain of E proteins. The strength of the binding of bHLH proteins to calmodulin correlates directly with the calmodulin sensitivity of their DNA binding. The basic sequence of MyoD, a class B protein, can also interact with calmodulin. This interaction, however, is blocked by MyoD sequences directly N-terminal of the basic sequence. We further demonstrate that S-100 proteins can interact with and differentially inhibit the DNA binding of bHLH proteins through interaction with the basic sequence. Both the binding to the basic sequence and the effect of the directly N-terminal sequence vary for different S-100 proteins and bHLH proteins. The results suggest the involvement of both calmodulin and S-100 proteins in the differential regulation of bHLH proteins.

[Indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center