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- 저자 : Braus, G.H. (검색결과 3 건)
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Sarikaya-Bayram, O.,Bayram, O.,Feussner, K.,Kim, J.H.,Kim, H.S.,Kaever, A.,Feussner, I.,Chae, K.S.,Han, D.M.,Han, K.H.,Braus, G.H. Cell Press 2014 DEVELOPMENTAL CELL Vol.29 No.4
Epigenetic and transcriptional control of gene expression must be coordinated in response to external signals to promote alternative multicellular developmental programs. The membrane-associated trimeric complex VapA-VipC-VapB controls a signal transduction pathway for fungal differentiation. The VipC-VapB methyltransferases are tethered to the membrane by the FYVE-like zinc finger protein VapA, allowing the nuclear VelB-VeA-LaeA complex to activate transcription for sexual development. Once the release from VapA is triggered, VipC-VapB is transported into the nucleus. VipC-VapB physically interacts with VeA and reduces its nuclear import and protein stability, thereby reducing the nuclear VelB-VeA-LaeA complex. Nuclear VapB methyltransferase diminishes the establishment of facultative heterochromatin by decreasing histone 3 lysine 9 trimethylation (H3K9me3). This favors activation of the regulatory genes brlA and abaA, which promote the asexual program. The VapA-VipC-VapB methyltransferase pathway combines control of nuclear import and stability of transcription factors with histone modification to foster appropriate differentiation responses.
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The Velvet Family of Fungal Regulators Contains a DNA-Binding Domain Structurally Similar to NF-κB
Ahmed, Yasar Luqman,Gerke, Jennifer,Park, Hee-Soo,Bayram, Ö,zgü,r,Neumann, Piotr,Ni, Min,Dickmanns, Achim,Kim, Sun Chang,Yu, Jae-Hyuk,Braus, Gerhard H.,Ficner, Ralf Public Library of Science 2013 PLoS biology Vol.11 No.12
<P>Morphological development of fungi and their combined production of secondary metabolites are both acting in defence and protection. These processes are mainly coordinated by <I>velvet</I> regulators, which contain a yet functionally and structurally uncharacterized <I>velvet</I> domain. Here we demonstrate that the <I>velvet</I> domain of VosA is a novel DNA-binding motif that specifically recognizes an 11-nucleotide consensus sequence consisting of two motifs in the promoters of key developmental regulatory genes. The crystal structure analysis of the VosA <I>velvet</I> domain revealed an unforeseen structural similarity with the Rel homology domain (RHD) of the mammalian transcription factor NF-κB. Based on this structural similarity several conserved amino acid residues present in all <I>velvet</I> domains have been identified and shown to be essential for the DNA binding ability of VosA. The <I>velvet</I> domain is also involved in dimer formation as seen in the solved crystal structures of the VosA homodimer and the VosA-VelB heterodimer. These findings suggest that defence mechanisms of both fungi and animals might be governed by structurally related DNA-binding transcription factors.</P><P><B>Author Summary</B></P><P>In many fungi, developmental processes and the synthesis of nonessential chemicals (secondary metabolites) are regulated by various external stimuli, such as light. Although fungi employ them for defensive purposes, secondary metabolites range from useful antibiotics to powerful toxins, so understanding the molecular processes that regulate their synthesis is of particular interest to us. In the mold <I>Aspergillus nidulans</I> the main regulators of these processes are the so-called “<I>velvet</I>” proteins VeA, VelB, and VosA, which share a 150-amino acid region known as the <I>velvet</I> domain. <I>Velvet</I> proteins interact with each other, alone (“homodimers”), in various combinations (“heterodimers”), and also with other proteins, but the molecular mechanism by which these proteins exert their regulatory function has been unclear. In this work we show that <I>velvet</I> proteins form a family of fungus-specific transcription factors that directly bind to target DNA, even though analysis of their amino acid sequence does not reveal any known DNA-binding domains or motifs. We determined the three-dimensional structure of the VosA-VosA homodimer and the VosA-VelB heterodimer and found that the structure of the <I>velvet</I> domain is strongly reminiscent of the N-terminal immunoglobulin-like domain found in the mammalian transcription factor NFκB-p50, despite the very low sequence similarity. We propose that, like NFκB, various homo- or heterodimers of <I>velvet</I> proteins modulate gene expression to drive development and defensive pathways in fungi.</P>
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Sarikaya Bayram, Ö,zlem,Bayram, Ö,zgü,r,Valerius, Oliver,Park, Hee Soo,Irniger, Stefan,Gerke, Jennifer,Ni, Min,Han, Kap-Hoon,Yu, Jae-Hyuk,Braus, Gerhard H. Public Library of Science 2010 PLoS genetics Vol.6 No.12
<▼1><P>VeA is the founding member of the velvet superfamily of fungal regulatory proteins. This protein is involved in light response and coordinates sexual reproduction and secondary metabolism in <I>Aspergillus nidulans</I>. In the dark, VeA bridges VelB and LaeA to form the VelB-VeA-LaeA (velvet) complex. The VeA-like protein VelB is another developmental regulator, and LaeA has been known as global regulator of secondary metabolism. In this study, we show that VelB forms a second light-regulated developmental complex together with VosA, another member of the velvet family, which represses asexual development. LaeA plays a key role, not only in secondary metabolism, but also in directing formation of the VelB-VosA and VelB-VeA-LaeA complexes. LaeA controls VeA modification and protein levels and possesses additional developmental functions. The <I>laeA</I> null mutant results in constitutive sexual differentiation, indicating that LaeA plays a pivotal role in inhibiting sexual development in response to light. Moreover, the absence of LaeA results in the formation of significantly smaller fruiting bodies. This is due to the lack of a specific globose cell type (Hülle cells), which nurse the young fruiting body during development. This suggests that LaeA controls Hülle cells. In summary, LaeA plays a dynamic role in fungal morphological and chemical development, and it controls expression, interactions, and modification of the velvet regulators.</P></▼1><▼2><P><B>Author Summary</B></P><P>Numerous fungi have the potential to infect immunocompromised patients or to contaminate and spoil our nutrients. They represent an increasing danger that threatens public health and agriculture. This requires improved understanding of fungal growth, development, dissemination of spores, and mycotoxin production. We have discovered two related fungal specific protein complexes that provide a molecular link among spore formation, fungal development, and secondary metabolite production. The subunit allocation of both complexes depends on each other, and they share a common subunit. These complexes comprise three related and in fungi conserved proteins of the velvet family that function in concert with a known regulator of secondary metabolism, LaeA. This protein controls the formation of both complexes but is only a part of the trimeric complex. We found that this regulator of secondary metabolism also possesses several developmental control functions in gene expression. These protein complexes discovered in the fungal model system <I>Aspergillus nidulans</I> are conserved in fungal pathogens where they might provide novel insights for understanding growth, development, and interaction with their respective hosts.</P></▼2>
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