Home About us Contact
|
Home About us Contact | ||
|
|
||
bHLH Domain (bhlh + domain)
Selected AbstractsIdentification of BOIP, a novel cDNA highly expressed during spermatogenesis that encodes a protein interacting with the orange domain of the hairy-related transcription factor HRT1/Hey1 in Xenopus and mouseDEVELOPMENTAL DYNAMICS, Issue 4 2003Reginald Van Wayenbergh Abstract Hairy-related transcription factor (HRT/Hey) genes encode a novel subfamily of basic helix-loop-helix (bHLH) transcription factors related to the Drosophila hairy and Enhancer-of-split (E(spl)) and the mammalian HES proteins that function as downstream mediators of Notch signaling. Using the yeast two-hybrid approach, a previously uncharacterized protein was identified in Xenopus that interacts with XHRT1 (originally referred to as bc8), one member of the HRT/Hey subclass. This protein is evolutionarily conserved in chordates. It binds to sequences adjacent to the bHLH domain of XHRT1 known as the Orange domain and has been named bc8 Orange interacting protein (BOIP). BOIP shows a rather uniform subcellular localization and is recruited to the nucleus upon binding to XHRT1. In Xenopus, XBOIP mRNA is detected by RNase protection analysis throughout embryogenesis. In the adult, the strongest expression is detected in testis. In the mouse, high levels of BOIP mRNA are also found in adult testis. No expression is detected in the embryo and in any of the other adult organs tested. In situ hybridization revealed that BOIP transcripts were detected almost exclusively in round spermatids and that this expression overlaps with that of Hey1 (HRT1), which is expressed throughout spermatogenesis. In view of the importance of the Orange domain for HRT/Hey function, the newly identified BOIP proteins may serve as regulators specifically of HRT1/Hey1 activity. Developmental Dynamics 228:716,725, 2003. © 2003 Wiley-Liss, Inc. [source] Spectroscopic and DNA-binding characterization of the isolated heme-bound basic helix,loop,helix-PAS-A domain of neuronal PAS protein 2 (NPAS2), a transcription activator protein associated with circadian rhythmsFEBS JOURNAL, Issue 11 2006Yuji Mukaiyama Neuronal PAS domain protein 2 (NPAS2) is a circadian rhythm-associated transcription factor with two heme-binding sites on two PAS domains. In the present study, we compared the optical absorption spectra, resonance Raman spectra, heme-binding kinetics and DNA-binding characteristics of the isolated fragment containing the N-terminal basic helix,loop,helix (bHLH) of the first PAS (PAS-A) domain of NPAS2 with those of the PAS-A domain alone. We found that the heme-bound bHLH-PAS-A domain mainly exists as a dimer in solution. The Soret absorption peak of the Fe(III) complex for bHLH-PAS-A (421 nm) was located at a wavelength 9 nm higher than for isolated PAS-A (412 nm). The axial ligand trans to CO in bHLH-PAS-A appears to be His, based on the resonance Raman spectra. In addition, the rate constant for heme association with apo-bHLH-PAS (3.3 × 107 mol,1·s,1) was more than two orders of magnitude higher than for association with apo-PAS-A (< 105 mol,1·s,1). These results suggest that the bHLH domain assists in stable heme binding to NPAS2. Both optical and resonance Raman spectra indicated that the Fe(II),NO heme complex is five-coordinated. Using the quartz-crystal microbalance method, we found that the bHLH-PAS-A domain binds specifically to the E-box DNA sequence in the presence, but not in the absence, of heme. On the basis of these results, we discuss the mode of heme binding by bHLH-PAS-A and its potential role in regulating DNA binding. [source] Hes7: a bHLH-type repressor gene regulated by Notch and expressed in the presomitic mesodermGENES TO CELLS, Issue 2 2001Yasumasa Bessho Background: Whereas Notch signalling is essential for somitogenesis, mice deficient for the basic helix-loop-helix (bHLH) genes Hes1 and Hes5, downstream Notch effectors, display normal somite formation, indicating that there may be an as-yet unidentified Hes1 -related bHLH gene. Results: We identified a novel bHLH gene, designated Hes7, from mouse embryos. Hes7 has a conserved bHLH domain in the amino-terminal region and the WRPW domain at the carboxy-terminal end, like Hes1. The mouse Hes7 gene is located next to Aloxe3, which is mapped to a position 37.0 cM from the centromere on chromosome 11. In a transfection analysis, Hes7 represses transcription from the N box- and E box-containing promoters. In addition, Hes7 suppresses the E47-induced transcriptional activation. Promoter analysis indicated that Hes7 expression is controlled by Notch signalling. Strikingly, Hes7 is specifically expressed in the presomitic mesoderm in a dynamic manner. We also identified two related bHLH genes from human: one is closely related to mouse Hes7 and therefore designated hHes7 and the other designated hHes4. Conclusion: The structure, transcriptional activity and expression pattern in the presomitic mesoderm of Hes7 are very similar to those of Hes1, suggesting that Hes7, together with Hes1, may play a role in somite formation under the control of Notch signalling. [source] Phytochrome-mediated inhibition of shade avoidance involves degradation of growth-promoting bHLH transcription factorsTHE PLANT JOURNAL, Issue 2 2008Séverine Lorrain Summary Plant growth and development are particularly sensitive to changes in the light environment and especially to vegetational shading. The shade-avoidance response is mainly controlled by the phytochrome photoreceptors. In Arabidopsis, recent studies have identified several related bHLH class transcription factors (PIF, for phytochrome-interacting factors) as important components in phytochrome signaling. In addition to a related bHLH domain, most of the PIFs contain an active phytochrome binding (APB) domain that mediates their interaction with light-activated phytochrome B (phyB). Here we show that PIF4 and PIF5 act early in the phytochrome signaling pathways to promote the shade-avoidance response. PIF4 and PIF5 accumulate to high levels in the dark, are selectively degraded in response to red light, and remain at high levels under shade-mimicking conditions. Degradation of these transcription factors is preceded by phosphorylation, requires the APB domain and is sensitive to inhibitors of the proteasome, suggesting that PIF4 and PIF5 are degraded upon interaction with light-activated phyB. Our data suggest that, in dense vegetation, which is rich in far-red light, shade avoidance is triggered, at least partially, as a consequence of reduced phytochrome-mediated degradation of transcription factors such as PIF4 and PIF5. Consistent with this idea, the constitutive shade-avoidance phenotype of phyB mutants partially reverts in the absence of PIF4 and PIF5. [source] | ||||||||||