Disease relevance of Helix-Loop-Helix Motifs

• The binding site contains the myc/HLH motif, CACGTG, and represents a 15 of 17 base match for the USF/MLTF binding site adjacent to the adenovirus major late promoter (MLP) [1].

Psychiatry related information on Helix-Loop-Helix Motifs

• MIDA1 associates with the HLH region of Id with the conserved region adjacent to eukaryotic DnaJ conserved motif within the Zuotin homology region, although it does not have any canonical HLH motif [2].

High impact information on Helix-Loop-Helix Motifs

• These oncogenes (Ttg1, Ttg2, SCL, LylI, H0X11) all belong to classic families of transcription factors, possessing LIM domains, helix-loop-helix motifs, or homeodomains [3].
• While the interactions between IKKalpha and IKKbeta may be mediated through their leucine zipper motifs, their helix-loop-helix motifs may be involved in interactions with essential regulatory subunits [4].
• A DNA binding and dimerization motif, with apparent amphipathic helices (the HLH motif), has recently been identified in various proteins, including two that bind to immunoglobulin enhancers (E12 and E47) [5].
• The Olf-1 protein, expressed exclusively in the olfactory receptor neurons and their precursors, contains a new helix-loop-helix motif and functions as an apparent homodimer [6].
• We have now investigated whether MyoD or myogenin, regulators of muscle-specific gene expression that have a helix-loop-helix motif, can induce the phenotypic conversion observed in heterokaryons [7].

Biological context of Helix-Loop-Helix Motifs

• Myc proteins have a tripartite carboxyl-terminal domain containing specific amino acid sequence motifs: a basic motif, a helix-loop-helix motif, and a leucine heptad repeat [8].
• Myogenin, MyoD, and a growing number of proteins implicated in transcriptional control share sequence homology within a basic region and an adjacent helix-loop-helix motif [9].
• Myogenin is a muscle-specific transcription factor that can activate myogenesis; it belongs to a family of transcription factors that share homology within a basic region and an adjacent helix-loop-helix (HLH) motif [10].
• Remarkably, however, digit duplication by dHAND requires neither the transcriptional activation domain nor the basic region, but only the HLH motif. eHAND has a similar limb patterning activity to dHAND in these misexpression experiments, indicating a conserved function of the HLH regions of these proteins [11].
• Interestingly, overexpression of Foxa2 activated the 18-bp enhancer in heterologous cells but only in the presence of the adjacent helix-loop-helix motif [12].

Associations of Helix-Loop-Helix Motifs with chemical compounds

• This structure consists of an arginine- and lysine-rich basic region followed by a helix-loop-helix motif, which together mediate specific binding to DNA [13].
• Both the first and second helices of the basic helix-loop-helix motif and the PAS region are required for dimerization [14].
• The 47-amino acid insertion contains a truncated phosphotyrosine interaction domain and a putative helix-loop-helix motif [15].
• The binding of N-acetylgalactosamine overlaps with that moiety of the T antigen, but surprisingly, N-acetylglucosamine, which differs from N-acetylgalactosamine only in the configuration of epimeric hydroxyl 4, binds at a totally different site on the opposite side of the helix-loop-helix motif [16].
• In earlier work, de novo designed peptides with a helix-loop-helix motif and 63 residues have been synthesized as potential scaffolds for stabilization of the [Ni(II)-X-Fe(4)S(4)] bridged assembly that is the spectroscopically deduced structure of the A-Cluster in clostridial carbon monoxide dehydrogenase [17].

Gene context of Helix-Loop-Helix Motifs

• Arnt contains a basic helix-loop-helix motif, which may be responsible for interacting with both the XRE and the ligand-binding subunit [18].
• This region of Rad18 contains a number of nonpolar residues that have been conserved in helix-loop-helix motifs of other proteins [19].
• A novel gene thus isolated is designated as Mesp1 and encodes a possible transcription factor MesP1 containing a basic helix-loop-helix motif [20].
• A novel E2F binding protein with Myc-type HLH motif stimulates E2F-dependent transcription by forming a heterodimer [21].
• Id is a nuclear factor containing a helix-loop-helix (HLH) motif [22].

Analytical, diagnostic and therapeutic context of Helix-Loop-Helix Motifs

• Sequence analysis of E2BP revealed 86.6% homology with a rat heterogeneous nuclear ribonucleoprotein C protein sequence, while conformational studies suggest a helix-loop-helix motif as a DNA-binding site [23].

References