A novel type of calmodulin interaction in the inhibition of basic helix-loop-helix transcription factors.
نویسندگان
چکیده
Calmodulin is the predominant intracellular receptor for Ca(2+) signals, mediating the regulation of numerous cellular processes. Previous studies have shown that calcium-loaded calmodulin can bind to and inhibit the activity of certain basic helix-loop-helix (bHLH) transcription factors. The basic sequence within the bHLH domain is the primary target for calmodulin binding, and sequences modulating the calmodulin interaction reside directly N-terminal to the basic sequence. Here we show that the interaction of calmodulin with bHLH proteins is of a novel type, displaying characteristics very different from those of previously characterized calmodulin-target complexes. We show that calmodulin interacts much stronger with a dimeric basic sequence than with the monomeric form. The calmodulin-bHLH protein complex contains equimolar amounts of calmodulin and bHLH chains. The interaction is unusual in being to a large extent polar in nature, and it is highly resistant to tested calmodulin inhibitors. Both the N-terminal and C-terminal domains of calmodulin can independently bind to and inhibit the DNA binding of bHLH proteins. The C-terminal domain preferentially binds to the basic sequence, whereas the N-terminal domain is essential for the effect of the modulatory sequence. We propose a model for the calmodulin-bHLH complex where two calmodulin molecules interact with one bHLH dimer, with one domain of calmodulin preferentially binding to the basic sequence of bHLH proteins and the other domain interacting with the modulatory sequence.
منابع مشابه
Calcium regulation of myogenesis by differential calmodulin inhibition of basic helix-loop-helix transcription factors.
The members of the MyoD family of basic helix-loop-helix (bHLH) transcription factors are critical regulators of skeletal muscle differentiation that function as heterodimers with ubiquitously expressed E-protein bHLH transcription factors. These heterodimers must compete successfully with homodimers of E12 and other E-proteins to enable myogenesis. Here, we show that E12 mutants resistant to C...
متن کاملA MODEL FOR THE BASIC HELIX- LOOPHELIX MOTIF AND ITS SEQUENCE SPECIFIC RECOGNITION OF DNA
A three dimensional model of the basic Helix-Loop-Helix motif and its sequence specific recognition of DNA is described. The basic-helix I is modeled as a continuous ?-helix because no ?-helix breaking residue is found between the basic region and the first helix. When the basic region of the two peptide monomers are aligned in the successive major groove of the cognate DNA, the hydrophobi...
متن کاملActivation of the myocyte enhancer factor-2 transcription factor by calcium/calmodulin-dependent protein kinase-stimulated binding of 14-3-3 to histone deacetylase 5.
Skeletal muscle differentiation is controlled by interactions between myocyte enhancer factor-2 (MEF2) and myogenic basic helix-loop-helix transcription factors. Association of MEF2 with histone deacetylases (HDAC) -4 and -5 results in repression of MEF2 target genes and inhibition of myogenesis. Calcium/calmodulin-dependent protein kinase (CaMK) signaling promotes myogenesis by disrupting MEF2...
متن کاملCalcium-dependent binding of Myc to calmodulin
The bHLH-LZ (basic region/helix-loop-helix/leucine zipper) oncoprotein Myc and the bHLH-LZ protein Max form a binary transcription factor complex controlling fundamental cellular processes. Deregulated Myc expression leads to neoplastic transformation and is a hallmark of most human cancers. The dynamics of Myc transcription factor activity are post-translationally coordinated by defined protei...
متن کاملFunctional Investigation of the Novel BRCA1variant (Glu1661Gly) byComputationalTools andYeastTranscription Activation Assay
Introduction: Mutations in the BRCA1 gene are major risk factors for breast and ovarian cancers. However, the relationship between some BRCA1 mutations and cancer risk remains largely unknown. Cancer risk predictions could be improved by evaluation of the impairment degree in the BRCA1 functions due to a specific mutation. This study aimed to assess the functional effect of a novel variant (Glu...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Biochemistry
دوره 39 15 شماره
صفحات -
تاریخ انتشار 2000