Iron is one of the essential mineral micronutrients for plants. Low concentrations of effective iron in soil can easily increase risk of plant iron deficiency. Several members of bHLH transcription factors family participate in the response to iron deficiency and play an important role in iron regulation of plants. In order to better understand the mechanism of iron deficiency response, an overview of the structure, classification, function and regulatory mechanism of bHLH transcription factors was given in this review as well as signaling pathway triggered by iron deficiency. It will provide theoretical basis and design strategies for cultivating iron deficiency tolerant or iron-rich crops using bHLH transcription factors.
Arabidopsis ; genetics ; metabolism ; Basic Helix-Loop-Helix Transcription Factors ; genetics ; metabolism ; Gene Expression Regulation, Plant ; Iron ; deficiency ; Signal Transduction ; physiology

The protein encoded by gene Nhlh2 (nescient helix-loop-helix 2, also known as HEN2 or NSCL2) is a new member of basic helix-loop-helix (bHLH) transcription factor family and is specifically expressed in nervous system, especially in neuroendocrine tissue. The homologous genes of Nhlh2 have been found in many eukaryotic organisms such as chicken, mouse, rat, cattle, and human. The functional researches of Nhlh2 are mainly focused on neuroendocrine system, retina development, and tumors. Some preliminary results have been obtained in the investigation of molecular regulation mechanism. This article summarizes the recent research advances in Nhlh2.
Animals ; Basic Helix-Loop-Helix Transcription Factors ; biosynthesis ; physiology ; Humans ; Neoplasms ; metabolism ; Nervous System ; metabolism ; Neurosecretory Systems ; metabolism ; Retina ; growth & development ; metabolism ; Species Specificity

More than 80% of all cases of deafness are related to the death or degeneration of cochlear hair cells and the associated spiral ganglion neurons, and a lack of regeneration of these cells leads to permanent hearing loss. Therefore, the regeneration of lost hair cells is an important goal for the treatment of deafness. Atoh1 is a basic helix-loop-helix (bHLH) transcription factor that is critical in both the development and regeneration of cochlear hair cells. Atoh1 is transcriptionally regulated by several signaling pathways, including Notch and Wnt signalings. At the post-translational level, it is regulated through the ubiquitin-proteasome pathway. In vitro and in vivo studies have revealed that manipulation of these signaling pathways not only controls development, but also leads to the regeneration of cochlear hair cells after damage. Recent progress toward understanding the signaling networks involved in hair cell development and regeneration has led to the development of new strategies to replace lost hair cells. This review focuses on our current understanding of the signaling pathways that regulate Atoh1 in the cochlea.
Basic Helix-Loop-Helix Transcription Factors/physiology* ; Cell Differentiation ; Cochlea/physiology* ; Hair Cells, Auditory/physiology* ; Hearing Loss/etiology* ; Humans ; Proteasome Endopeptidase Complex/physiology* ; Signal Transduction/physiology* ; Transcription Factors/physiology* ; Ubiquitin/metabolism* ; Wnt Signaling Pathway ; beta Catenin/physiology*

Animals ; Basic Helix-Loop-Helix Transcription Factors ; physiology ; Chronic Disease ; Humans ; Hypoxia ; complications ; Hypoxia-Inducible Factor 1 ; physiology ; Kidney ; metabolism ; Kidney Diseases ; etiology ; Oxidative Stress ; Procollagen-Proline Dioxygenase ; physiology

Low density lipoprotein receptor (LDLR) plays an important role in the cholesterol homeostasis. We examined the possible circadian regulation of LDLR and mechanism(s) underlying it. In mice, blood glucose and plasma triglyceride, total and high density lipoprotein cholesterol varied distinctively throughout a day. In addition, LDLR mRNA oscillated in the liver in a functional clock-dependent manner. Accordingly, analysis of human LDLR promoter sequence revealed three putative E-boxes, raising the possible regulation of LDLR expression by E-box-binding transcription factors. To test this possibility, human LDLR promoter reporter constructs were transfected into HepG2 cells and the effects of CLOCK/BMAL1, Hes1, and Hes6 expression were analyzed. It was found that positive circadian transcription factor complex CLOCK/BMAL1 upregulated human LDLR promoter activity in a serum-independent manner, while Hes family members Hes1 and Hes6 downregulated it only under serum-depleted conditions. Both effects were mapped to proximal promoter region of human LDLR, where mutation or deletion of well-known sterol regulatory element (SRE) abolished only the repressive effect of Hes1. Interestingly, hes6 and hes1 mRNA oscillated in an anti-phasic manner in the wild-type but not in the per1-/-per2-/- mouse. Comparative analysis of mouse, rat and human hes6 genes revealed that three E-boxes are conserved among three species. Transfection and site-directed mutagenesis studies with hes6 reporter constructs confirmed that the third E-box in the exon IV is functionally induced by CLOCK/BMAL1. Taken together, these results suggest that LDLR expression is under circadian control involving CLOCK/BMAL1 and Hes family members Hes1 and Hes6.
ARNTL Transcription Factors/physiology ; Animals ; Base Sequence ; Basic Helix-Loop-Helix Transcription Factors/*genetics/metabolism/physiology ; CLOCK Proteins/physiology ; Cholesterol/blood ; *Circadian Rhythm ; E-Box Elements ; Exons ; *Gene Expression Regulation ; Hep G2 Cells ; Homeodomain Proteins/*genetics/metabolism/physiology ; Homeostasis ; Humans ; Liver/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; *Promoter Regions, Genetic ; Receptors, LDL/*genetics/metabolism ; Repressor Proteins/*genetics/metabolism/physiology ; Transcription, Genetic

Animals ; Basic Helix-Loop-Helix Transcription Factors ; metabolism ; physiology ; Cadherins ; metabolism ; Cell Transformation, Neoplastic ; metabolism ; pathology ; Epithelial Cells ; pathology ; Homeodomain Proteins ; metabolism ; physiology ; Humans ; Mesenchymal Stromal Cells ; pathology ; Neoplasm Invasiveness ; Neoplasm Metastasis ; Neoplasms ; metabolism ; pathology ; Snail Family Transcription Factors ; Transcription Factors ; metabolism ; physiology ; Zinc Finger E-box-Binding Homeobox 1

BACKGROUNDDelta-like 4 (DLL4) is an endothelium specific Notch ligand and has been shown to function as a regulating factor during physiological and pathological angiogenesis. It has been reported that the DLL4-Notch signaling pathway is regulated by hypoxia and may prevent excessive angiogenesis through the inhibition of angiogenic branching and by triggering vessel maturation. Choroidal neovascularization (CNV) is a pathological form of angiogenesis in which hypoxia is thought to play an important role. This study was aimed to evaluate the role of DLL4 in the development of CNV.

METHODSWe utilized chemical hypoxia induced by 200 µmol/L CoCl2 to observe the expression of DLL4 in choroid-retinal endothelial cells (RF/6A cells), which are the primary cells involved in CNV. After transfection of a DLL4 small interfering RNA (siRNA), mRNA and protein expression of DLL4 and key downstream genes, including HES1 and HEY1, in hypoxic RF/6A cells were investigated by RT-PCR, real-time PCR, and Western blotting analysis. Three controls were used: one without transfection, one with transfection reagent, and one with scrambled negative control siRNA. The effects of the DLL4 siRNA on the biological function of hypoxic RF/6A cells during angiogenesis, including cell proliferation, migration and tube formation, were investigated.

RESULTSThe results showed that hypoxic conditions led to upregulation of DLL4 expression in RF/6A cells in vitro. After transfection, siRNA-duplex1 targeting DLL4 depleted the DLL4 mRNA levels by as much as 91.4% compared with the scrambled siRNA control, and DLL4 protein expression was similarly effected. There was no significant difference in DLL4 expression among the blank control, transfection reagent control, and scrambled siRNA groups. In addition, after transfection of hypoxic RF/6A cells with the DLL4 siRNA-duplex1, the mRNA levels of HES1 and HEY1, which function downstream of DLL4-Notch signaling, were lowered by 75.1% and 86.3%, respectively, compared with the scrambled siRNA control. Furthermore, knockdown of DLL4 expression significantly promoted the proliferation of hypoxic RF/6A cells and led to their arrest in the S phase of the cell cycle. Migration and tube formation of hypoxic RF/6A cells were significantly induced by the DLL4 siRNA, with the number of migrated cells increased by 1.6-fold and total tube length increased by 82.3%, compared with the scrambled siRNA (P < 0.05).

CONCLUSIONSDLL4 functions as a negative regulator of angiogenic branching and sprouting. Based on our results, DLL4 signaling appears to play an essential role in the biological behavior of choroid vascular endothelial cells under hypoxia. Therefore, DLL4 may represent a novel target for CNV therapy in the future.

Basic Helix-Loop-Helix Transcription Factors ; genetics ; metabolism ; Blotting, Western ; Cell Cycle ; genetics ; physiology ; Cell Cycle Proteins ; genetics ; metabolism ; Cell Hypoxia ; genetics ; physiology ; Cell Line ; Cell Movement ; genetics ; physiology ; Cell Proliferation ; Choroidal Neovascularization ; Endothelial Cells ; cytology ; metabolism ; Homeodomain Proteins ; genetics ; metabolism ; Humans ; Intercellular Signaling Peptides and Proteins ; genetics ; metabolism ; RNA, Small Interfering ; Reverse Transcriptase Polymerase Chain Reaction ; Transcription Factor HES-1

OBJECTIVETo investigate the status of Notch signaling pathway in small cell lung cancer (SCLC).

METHODSExpression plasmids of pEFBOS-NIC-MYC and pEFBOS-neo were transfected into NCI-H446 cells. Stably transfected cell lines were selected and their growth rates were examined by MTT method. Expression of downstream genes along the Notch signaling pathway were studied by RT-PCR. Protein expression of euroendocrine markers of CgA and NSE were detected by Western blot analysis and immunocytochemistry.

RESULTSThe expression of HES1 was increased in the pEFBOS-NIC-MYC group, but the expression of hASH in the pEFBOS-NIC-MYC group was decreased significantly. The transfected cells with pEFBOS-NIC-MYC plasmid showed a significantly slower growth rate compared with that of two control groups (P < 0.05, Student's t-test). Immunocytochemistry of NSE showed that PUs in the NIC transfected group, sham group and negative control group were 7.21 ± 0.59, 28.25 ± 1.46, 30.57 ± 1.31 respectively, the former one was smaller than the values of the latter two significantly (P < 0.01). Western blot analysis showed the grave scales of CgA in NIC transfected group and sham group to be 0.54 ± 0.03 and 0.99 ± 0.05 respectively (grave scales of the negative control was set as 1.00), the former one significantly smaller than that of the other two groups (P < 0.01). The grave scales of NSE in the NIC transfected group and sham group were 0.43 ± 0.02 and 1.07 ± 0.09 respectively (grave scales of the negative control was set as 1.00) and the former one was significantly smaller than the other two groups (P < 0.01).

CONCLUSIONNotch signaling pathway regulates SCLC cells through its inhibitory effect on hASH1 transcription via HES1 along with an expression inhibition of neuroendocrine markers in SCLC.

Basic Helix-Loop-Helix Transcription Factors ; metabolism ; Cell Line, Tumor ; Cell Proliferation ; Chromogranin A ; metabolism ; Homeodomain Proteins ; metabolism ; Humans ; Lung Neoplasms ; metabolism ; pathology ; Phosphopyruvate Hydratase ; metabolism ; Plasmids ; Receptor, Notch1 ; metabolism ; physiology ; Recombinant Proteins ; metabolism ; Signal Transduction ; Small Cell Lung Carcinoma ; metabolism ; pathology ; Transcription Factor HES-1 ; Transfection

OBJECTIVE: To investigate the role of Notch signaling in differentiation of Sprague-Dawley (SD) rat retinal progenitor cells (RPCs). METHODS: RPCs were isolated from 16-day embryonic SD rats and cultured in suspension. RPCs were cultured respectively in media with (treatment group) or without (control group) gamma-secretase inhibitor X which was used to block Notch signaling. Morphological observation and immunocytochemistry were applied at day 14 to determine the cell types and analyze the expression of Notch pathway genes in both groups. RESULTS: Most RPCs expressed Notch1 intracellular domains or its downstream transcriptional factor Hes1. A few expressed bHLH transcriptional factors NeuroD and Mash1. Most auto-differentiated RPCs expressed NeuroD or Mash1, while a few of them expressed Notch1 intracellular domains or Hes1. In the group treated with gamma-secretase inhibitor X, the positive rate of Nestin or GFAP was much lower than that in the control group while the positive rate of beta-tubulin was much higher than that in the control group. The difference in the positive rate of recovering between the two groups was not significant. CONCLUSION In vitro Notch signaling may inhibit retinal stem cells differentiation. Inhibiting Notch signaling in vitro may promote differentiation to neurons and partially inhibit glial differentiation.
Animals ; Basic Helix-Loop-Helix Transcription Factors ; metabolism ; Cell Differentiation ; physiology ; Cells, Cultured ; Female ; Fetus ; Homeodomain Proteins ; metabolism ; Neurons ; cytology ; Rats ; Rats, Sprague-Dawley ; Receptor, Notch1 ; genetics ; metabolism ; Retina ; cytology ; Signal Transduction ; drug effects ; physiology ; Stem Cells ; cytology ; Transcription Factor HES-1

BACKGROUNDThe tendency of tumor cells to disperse throughout the liver is a distinct feature of hepatocellular carcinoma (HCC). Nck family adaptor proteins function to regulate actin cytoskeletal reorganization that leads to cell motility. We previously found that Max binding protein (MNT) was differentially expressed in HCC, and interacted with Nck1 by 2-DE. MNT is a protein member of the Myc/Max/Mad network which plays roles in cell proliferation, differentiation, and death. We investigated the effects of MNT on migration of human liver cancer SK-HEP-1 cells to study the migration regulatory role of MNT in HCC cells.

METHODSInteraction between MNT and Nck1 was further validated in hepatoma cells by GST-pull down assay and immunoprecipitation. siRNAs specific to MNT (MNT siRNA) were used to knockdown MNT expression. Western blotting, transwell assay were used to determine the migration potential of cells.

RESULTSInteraction between MNT and Nck1 was validated in hepatoma cells. MNT knockdown promoted the migration of human liver cancer SK-HEP-1 cells (P < 0.01).

CONCLUSIONThe results suggest that MNT, via interaction with Nck1, inhibits hepatoma cell migration.

Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors ; genetics ; metabolism ; Blotting, Western ; Cell Differentiation ; genetics ; physiology ; Cell Line, Tumor ; Cell Movement ; genetics ; physiology ; Humans ; Immunoprecipitation ; Liver Neoplasms ; Oncogene Proteins ; genetics ; metabolism ; Protein Binding ; genetics ; physiology ; Repressor Proteins ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction