scholarly journals Role of a versatile peptide motif in controlling Hox nuclear export and autophagy in the Drosophila fat body

2019 ◽  
Author(s):  
Marilyne Duffraisse ◽  
Rachel Paul ◽  
Bruno Hudry ◽  
Julie Carnesecchi ◽  
Agnes Banretti ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Target Genes ◽  
Fat Body ◽  
Nuclear Export Signal ◽  
Peptide Motif ◽  
Linear Motif ◽  
Hox Proteins ◽  
Downstream Target ◽  
Transcriptional Cofactors ◽  
Hox Protein

Hox proteins are major regulators of embryonic development, acting in the nucleus to regulate the expression of their numerous downstream target genes. By analyzing deleted forms of the Drosophila Hox protein Ultrabithorax (Ubx), we revealed the presence of an unconventional Nuclear Export Signal (NES) that overlaps with the highly conserved hexapeptide (HX) motif. This short linear motif was originally described as mediating the interaction with the PBC proteins, a generic and crucial class of Hox transcriptional cofactors in development and cancer. Here we show that the HX motif is involved in the interaction with the major CRM1/Embargoed exportin protein. This novel role was found in several Drosophila and human Hox proteins. We provide evidence that HX-dependent Hox nuclear export is tightly regulated in the Drosophila fat body to control the onset of autophagy. Our results underline the high molecular versatility of a unique short peptide motif for controlling context-dependent activity of Hox proteins at both transcriptional and non-transcriptional levels.

scholarly journals Role of a versatile peptide motif controlling Hox nuclear export and autophagy in the Drosophila fat body

2020 ◽  
Vol 133 (18) ◽  
pp. jcs241943
Author(s):  
Marilyne Duffraisse ◽  
Rachel Paul ◽  
Julie Carnesecchi ◽  
Bruno Hudry ◽  
Agnes Banreti ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Target Genes ◽  
Fat Body ◽  
Nuclear Export Signal ◽  
Peptide Motif ◽  
Hox Proteins ◽  
Downstream Target

ABSTRACTHox proteins are major regulators of embryonic development, acting in the nucleus to regulate the expression of their numerous downstream target genes. By analyzing deletion forms of the Drosophila Hox protein Ultrabithorax (Ubx), we identified the presence of an unconventional nuclear export signal (NES) that overlaps with a highly conserved motif originally described as mediating the interaction with the PBC proteins, a generic and crucial class of Hox transcriptional cofactors that act in development and cancer. We show that this unconventional NES is involved in the interaction with the major exportin protein CRM1 (also known as Embargoed in flies) in vivo and in vitro. We find that this interaction is tightly regulated in the Drosophila fat body to control the autophagy-repressive activity of Ubx during larval development. The role of the PBC interaction motif as part of an unconventional NES was also uncovered in other Drosophila and human Hox proteins, highlighting the evolutionary conservation of this novel function. Together, our results reveal the extreme molecular versatility of a unique short peptide motif for controlling the context-dependent activity of Hox proteins both at transcriptional and non-transcriptional levels.

scholarly journals A novel LIM protein Cal promotes cardiac differentiation by association with CSX/NKX2-5

2004 ◽  
Vol 164 (3) ◽  
pp. 395-405 ◽  
Author(s):  
Hiroshi Akazawa ◽  
Sumiyo Kudoh ◽  
Naoki Mochizuki ◽  
Noboru Takekoshi ◽  
Hiroyuki Takano ◽  
...  
Keyword(s):  
Heart Development ◽  
Nuclear Export ◽  
Target Genes ◽  
Nuclear Export Signal ◽  
Gene Promoter ◽  
Myocardial Cell ◽  
Cardiac Differentiation ◽  
Lim Protein

The cardiac homeobox transcription factor CSX/NKX2-5 plays an important role in vertebrate heart development. Using a yeast two-hybrid screening, we identified a novel LIM domain–containing protein, named CSX-associated LIM protein (Cal), that interacts with CSX/NKX2-5. CSX/NKX2-5 and Cal associate with each other both in vivo and in vitro, and the LIM domains of Cal and the homeodomain of CSX/NKX2-5 were necessary for mutual binding. Cal itself possessed the transcription-promoting activity, and cotransfection of Cal enhanced CSX/NKX2-5–induced activation of atrial natriuretic peptide gene promoter. Cal contained a functional nuclear export signal and shuttled from the cytoplasm into the nucleus in response to calcium. Accumulation of Cal in the nucleus of P19CL6 cells promoted myocardial cell differentiation accompanied by increased expression levels of the target genes of CSX/NKX2-5. These results suggest that a novel LIM protein Cal induces cardiomyocyte differentiation through its dynamic intracellular shuttling and association with CSX/NKX2-5.

Hox repression of a target gene: extradenticle-independent, additive action through multiple monomer binding sites

Development ◽  
2002 ◽  
Vol 129 (13) ◽  
pp. 3115-3126 ◽  
Author(s):  
Ron Galant ◽  
Christopher M. Walsh ◽  
Sean B. Carroll
Keyword(s):  
Binding Sites ◽  
Target Gene ◽  
Target Genes ◽  
Hox Genes ◽  
Regulatory Element ◽  
Morphological Diversity ◽  
Hox Proteins ◽  
Cis Element ◽  
Additive Action ◽  
Hox Protein

Homeotic (Hox) genes regulate the identity of structures along the anterior-posterior axis of most animals. The low DNA-binding specificities of Hox proteins have raised the question of how these transcription factors selectively regulate target gene expression. The discovery that the Extradenticle (Exd)/Pbx and Homothorax (Hth)/Meis proteins act as cofactors for several Hox proteins has advanced the view that interactions with cofactors are critical to the target selectivity of Hox proteins. It is not clear, however, to what extent Hox proteins also regulate target genes in the absence of cofactors. In Drosophila melanogaster, the Hox protein Ultrabithorax (Ubx) promotes haltere development and suppresses wing development by selectively repressing many genes of the wing-patterning hierarchy, and this activity requires neither Exd nor Hth function. Here, we show that Ubx directly regulates a flight appendage-specific cis-regulatory element of the spalt (sal) gene. We find that multiple monomer Ubx-binding sites are required to completely repress this cis-element in the haltere, and that individual Ubx-binding sites are sufficient to mediate its partial repression. These results suggest that Hox proteins can directly regulate target genes in the absence of the cofactor Extradenticle. We propose that the regulation of some Hox target genes evolves via the accumulation of multiple Hox monomer binding sites. Furthermore, because the development and morphological diversity of the distal parts of most arthropod and vertebrate appendages involve Hox, but not Exd/Pbx or Hth/Meis proteins, this mode of target gene regulation appears to be important for distal appendage development and the evolution of appendage diversity.

The lines gene of Drosophila is required for specific functions of the Abdominal-B HOX protein

Development ◽  
1998 ◽  
Vol 125 (7) ◽  
pp. 1269-1274 ◽  
Author(s):  
J. Castelli-Gair
Keyword(s):  
Hox Genes ◽  
Hox Proteins ◽  
Normal Functions ◽  
Transcriptional Cofactors ◽  
Segment Polarity ◽  
Direct Target ◽  
Hox Protein ◽  
Segment Polarity Gene ◽  
Anterior Posterior ◽  
Polarity Gene

The Hox genes encode homeobox transcription factors that control the formation of segment specific structures in the anterior-posterior axis. HOX proteins regulate the transcription of downstream targets acting both as repressors and as activators. Due to the similarity of their homeoboxes it is likely that much of the specificity of HOX proteins is determined by interaction with transcriptional cofactors, but few HOX cofactor proteins have yet been described. Here I present genetic evidence showing that lines, a segment polarity gene of Drosophila, is required for the function of the Abdominal-B protein. In lines mutant embryos Abdominal-B protein expression is normal but incapable of promoting its normal functions: formation of the posterior spiracles and specification of an eighth abdominal denticle belt. These defects arise because in lines mutant embryos the Abdominal-B protein cannot activate its direct target empty spiracles or other downstream genes while it can function as a repressor of Ultrabithorax and abdominal-A. The lines gene seems to be required exclusively for Abdominal-B but not for the function of other Hox genes.

scholarly journals Baicalin alleviates hyperglycemia-induced endothelial impairment via Nrf2

2019 ◽  
Vol 240 (1) ◽  
pp. 81-98 ◽  
Author(s):  
Gen Chen ◽  
Xiangjuan Chen ◽  
Chao Niu ◽  
Xiaozhong Huang ◽  
Ning An ◽  
...  
Keyword(s):  
Oxidative Damage ◽  
Nuclear Export ◽  
Target Genes ◽  
Ex Vivo ◽  
Umbilical Vein ◽  
Protective Effects ◽  
Cellular Mechanisms ◽  
Downstream Target ◽  
Nrf2 Activation

Baicalin is the major component found in Scutellaria baicalensis root, a widely used herb in traditional Chinese medicine, which exhibits strong anti-inflammatory, anti-viral and anti-tumor activities. The present work was devoted to elucidate the molecular and cellular mechanisms underlying the protective effects of Baicalin against diabetes-induced oxidative damage, inflammation and endothelial dysfunction. Diabetic mice, induced by streptozotocin (STZ), were treated with intraperitoneal Baicalin injections. Human umbilical vein endothelial cells (HUVECs) were cultured either in normal glucose (NG, 5.5 mM) or high glucose (HG, 33 mM) medium in the presence or absence of Baicalin for 72 h. We observed an obvious inhibition of hyperglycemia-triggered oxidative damage and inflammation in HUVECs and diabetic aortal vasculature by Baicalin, along with restoration of hyperglycemia-impaired nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway activity. However, the protective effects of Baicalin almost completely abolished in HUVECs transduced with shRNA against Nrf2, but not with nonsense shRNA. Mechanistic studies demonstrated that HG decreased Akt and GSK3B phosphorylation, restrained nuclear export of Fyn and nuclear localization of Nrf2, blunted Nrf2 downstream target genes and subsequently induced oxidative stress in HUVECs. However, those destructive cascades were well prevented by Baicalin in HUVECs. Furthermore, LY294002 and ML385 (inhibitor of PI3K and Nrf2) attenuated Baicalin-mediated Nrf2 activation and the ability of facilitates angiogenesis in vivo and ex vivo. Taken together, the endothelial protective effect of Baicalin under hyperglycemia condition could be partly attributed to its role in downregulating reactive oxygen species (ROS) and inflammation via the Akt/GSK3B/Fyn-mediated Nrf2 activation.

scholarly journals Definition of the Transcriptional Activation Domains of Three Human HOX Proteins Depends on the DNA-Binding Context

1998 ◽  
Vol 18 (11) ◽  
pp. 6201-6212 ◽  
Author(s):  
Maria Alessandra Viganò ◽  
Giuliana Di Rocco ◽  
Vincenzo Zappavigna ◽  
Fulvio Mavilio
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Regulatory Elements ◽  
Hox Proteins ◽  
Activation Domains ◽  
Downstream Target ◽  
Transcriptional Machinery ◽  
Transcriptional Activation Domains

ABSTRACT Hox proteins control developmental patterns and cell differentiation in vertebrates by acting as positive or negative regulators of still unidentified downstream target genes. The homeodomain and other small accessory sequences encode the DNA-protein and protein-protein interaction functions which ultimately dictate target recognition and functional specificity in vivo. The effector domains responsible for either positive or negative interactions with the cell transcriptional machinery are unknown for most Hox proteins, largely due to a lack of physiological targets on which to carry out functional analysis. We report the identification of the transcriptional activation domains of three human Hox proteins, HOXB1, HOXB3, and HOXD9, which interact in vivo with the autoregulatory and cross-regulatory enhancers of the murine Hoxb-1 and human HOXD9 genes. Activation domains have been defined both in a homologous context, i.e., within a HOX protein binding as a monomer or as a HOX-PBX heterodimer to the specific target, and in a heterologous context, after translocation to the yeast Gal4 DNA-binding domain. Transfection analysis indicates that activation domains can be identified in different regions of the three HOX proteins depending on the context in which they interact with the DNA target. These results suggest that Hox proteins may be multifunctional transcriptional regulators, interacting with different cofactors and/or components of the transcriptional machinery depending on the structure of their target regulatory elements.

scholarly journals A Hox-Eya-Pax Complex Regulates Early Kidney Developmental Gene Expression

2007 ◽  
Vol 27 (21) ◽  
pp. 7661-7668 ◽  
Author(s):  
Ke-Qin Gong ◽  
Alisha R. Yallowitz ◽  
Hanshi Sun ◽  
Gregory R. Dressler ◽  
Deneen M. Wellik
Keyword(s):  
Target Genes ◽  
Kidney Development ◽  
Metanephric Mesenchyme ◽  
Hox Proteins ◽  
Downstream Target ◽  
Developmental Gene Expression ◽  
Dna Binding Specificity ◽  
Mesoderm Specification ◽  
Anterior Posterior

ABSTRACT During embryonic development, the anterior-posterior body axis is specified in part by the combinatorial activities of Hox genes. Given the poor DNA binding specificity of Hox proteins, their interaction with cofactors to regulate target genes is critical. However, few regulatory partners or downstream target genes have been identified. Herein, we demonstrate that Hox11 paralogous proteins form a complex with Pax2 and Eya1 to directly activate expression of Six2 and Gdnf in the metanephric mesenchyme. We have identified the binding site within the Six2 enhancer necessary for Hox11-Eya1-Pax2-mediated activation and demonstrate that this site is essential for Six2 expression in vivo. Furthermore, genetic interactions between Hox11 and Eya1 are consistent with their participation in the same pathway. Thus, anterior-posterior-patterning Hox proteins interact with Pax2 and Eya1, factors important for nephrogenic mesoderm specification, to directly regulate the activation of downstream target genes during early kidney development.

scholarly journals Sox10 Is an Active Nucleocytoplasmic Shuttle Protein, and Shuttling Is Crucial for Sox10-Mediated Transactivation

2002 ◽  
Vol 22 (16) ◽  
pp. 5826-5834 ◽  
Author(s):  
Stephan Rehberg ◽  
Peter Lischka ◽  
Gabi Glaser ◽  
Thomas Stamminger ◽  
Michael Wegner ◽  
...  
Keyword(s):  
Dna Binding ◽  
Nuclear Export ◽  
Target Genes ◽  
Nuclear Export Signal ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Nucleocytoplasmic Shuttling ◽  
Nucleocytoplasmic Shuttle ◽  
Nuclear Localization Signals ◽  
Export Signal

ABSTRACT Sox10 belongs to a family of transcription regulators characterized by a DNA-binding domain known as the HMG box. It plays fundamental roles in neural crest development, peripheral gliogenesis, and terminal differentiation of oligodendrocytes. In accord with its function as transcription factor, Sox10 contains two nuclear localization signals and is most frequently detected in the nucleus. In this study, we report that Sox10 is an active nucleocytoplasmic shuttle protein, competent of both entering and exiting the nucleus. We identified a functional Rev-type nuclear export signal within the DNA-binding domain of Sox10. Mutational inactivation of this nuclear export signal or treatment of cells with the CRM1-specific export inhibitor leptomycin B inhibited nuclear export and consequently nucleocytoplasmic shuttling of Sox10. Importantly, the inhibition of the nuclear export of Sox10 led to decreased transactivation of transfected reporters and endogenous target genes, arguing that continuous nucleocytoplasmic shuttling is essential for the function of Sox10. To our knowledge this is the first time that nuclear export has been reported and shown to be functionally relevant for any Sox protein.

scholarly journals Postrepression Activation of NF-κB Requires the Amino-Terminal Nuclear Export Signal Specific to IκBα

2001 ◽  
Vol 21 (14) ◽  
pp. 4737-4747 ◽  
Author(s):  
Tony T. Huang ◽  
Shigeki Miyamoto
Keyword(s):  
Nuclear Export ◽  
Mammalian Cells ◽  
Target Genes ◽  
Nuclear Export Signal ◽  
Feedback Regulation ◽  
Mechanistic Explanation ◽  
Binding Activity ◽  
Critical Event ◽  
Specific Function ◽  
Amino Terminal

ABSTRACT One of the most prominent NF-κB target genes in mammalian cells is the gene encoding one of its inhibitor proteins, IκBα. The increased synthesis of IκBα leads to postinduction repression of nuclear NF-κB activity. However, it is unknown why IκBα, among multiple IκB family members, is involved in this process and what significance this feedback regulation has beyond terminating NF-κB activity. Herein, we report an important IκBα-specific function dictated by its amino-terminal nuclear export sequence (N-NES). The IκBα N-NES is necessary for the postinduction export of nuclear NF-κB, which is a critical event in reestablishing a permissive condition for NF-κB to be rapidly reactivated. We show that although IκBα and another IκB member, IκBβ, can enter the nucleus and repress NF-κB DNA-binding activity during the postinduction phase, only IκBα allows the efficient export of nuclear NF-κB. Moreover, swapping the N-terminal region of IκBβ for the corresponding IκBα sequence is sufficient for the IκB chimera protein to export NF-κB similarly to IκBα during the postinduction state. Our findings provide a mechanistic explanation of why IκBα but not other IκB members is crucial for postrepression activation of NF-κB. We propose that this IκBα-specific function is important for certain physiological and pathological conditions where NF-κB needs to be rapidly reactivated.

scholarly journals Nucleo-cytoplasmic shuttling of murine RBPJ by Hairless protein matches that of Su(H) protein in the model system Drosophila melanogaster

Hereditas ◽  
2021 ◽  
Vol 158 (1) ◽  
Author(s):  
Dorina B. Wolf ◽  
Dieter Maier ◽  
Anja C. Nagel
Keyword(s):  
Notch Signaling ◽  
Nuclear Import ◽  
Subcellular Distribution ◽  
Nuclear Export ◽  
Target Genes ◽  
Nuclear Export Signal ◽  
Notch Signaling Pathway ◽  
Nuclear Entry ◽  
Protein Variant ◽  
Signaling Activity

Abstract CSL transcription factors are central to signal transduction in the highly conserved Notch signaling pathway. CSL acts as a molecular switch: depending on the cofactors recruited, CSL induces either activation or repression of Notch target genes. Unexpectedly, CSL depends on its cofactors for nuclear entry, despite its role as gene regulator. In Drosophila, the CSL homologue Suppressor of Hairless (Su(H)), recruits Hairless (H) for repressor complex assembly, and eventually for nuclear import. We recently found that Su(H) is subjected to a dynamic nucleo-cytoplasmic shuttling, thereby strictly following H subcellular distribution. Hence, regulation of nuclear availability of Su(H) by H may represent a new layer of control of Notch signaling activity. Here we extended this work on the murine CSL homologue RBPJ. Using a ‘murinized’ fly model bearing RBPJwt in place of Su(H) at the endogenous locus we demonstrate that RBPJ protein likewise follows H subcellular distribution. For example, overexpression of a H*NLS3 protein variant defective of nuclear import resulted in a cytosolic localization of RBPJ protein, whereas the overexpression of a H*NES protein variant defective in the nuclear export signal caused the accumulation of RBPJ protein in the nucleus. Evidently, RBPJ is exported from the nucleus as well. Overall these data demonstrate that in our fly model, RBPJ is subjected to H-mediated nucleo-cytoplasmic shuttling as is Su(H). These data raise the possibility that nuclear availability of mammalian CSL proteins is likewise restricted by cofactors, and may hence present a more general mode of regulating Notch signaling activity. Graphical abstract

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