| 1. |
- Hillier, Ladeana W, et al.
(author)
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Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution
- 2004
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In: Nature. - 0028-0836 .- 1476-4687. ; 432:7018, s. 695-716
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Journal article (peer-reviewed)abstract
- We present here a draft genome sequence of the red jungle fowl, Gallus gallus. Because the chicken is a modern descendant of the dinosaurs and the first non-mammalian amniote to have its genome sequenced, the draft sequence of its genome--composed of approximately one billion base pairs of sequence and an estimated 20,000-23,000 genes--provides a new perspective on vertebrate genome evolution, while also improving the annotation of mammalian genomes. For example, the evolutionary distance between chicken and human provides high specificity in detecting functional elements, both non-coding and coding. Notably, many conserved non-coding sequences are far from genes and cannot be assigned to defined functional classes. In coding regions the evolutionary dynamics of protein domains and orthologous groups illustrate processes that distinguish the lineages leading to birds and mammals. The distinctive properties of avian microchromosomes, together with the inferred patterns of conserved synteny, provide additional insights into vertebrate chromosome architecture.
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| 2. |
- Deleuil, Fabienne, et al.
(author)
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Interaction between the Yersinia protein tyrosine phosphatase YopH and eukaryotic Cas/Fyb is an important virulence mechanism
- 2003
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In: Cellular Microbiology. - : Blackwell Publishing. - 1462-5814 .- 1462-5822. ; 5:1, s. 53-64
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Journal article (peer-reviewed)abstract
- The tyrosine phosphatase YopH is an essential virulence factor produced by pathogenic Yersinia species. YopH is translocated into host cells via a type III secretion system and its dephosphorylating activity causes disruption of focal complex structures and blockage of the phagocytic process. Among the host cell targets of YopH are the focal adhesion proteins Crk-associated substrate (p130Cas) and focal adhesion kinase (FAK) in epithelial cells, and p130Cas and Fyn-binding protein (Fyb) in macrophages. Previous studies have shown that the N-terminal domain of YopH acts as a substrate-binding domain. In this study, the mechanism and biological importance of the targeting of YopH to focal complexes relative to its interaction with p130Cas/Fyb was elucidated. Mutants of YopH that were defective in p130Cas/Fyb binding but otherwise indistinguishable from wild type were constructed. Mutants unable to bind p130Cas did not localize to focal complex structures in infected cells, indicating that the association with p130Cas is critical for appropriate subcellular localization of YopH. These yopH mutants were also clearly attenuated in virulence, showing that binding to p130Cas and/or Fyb is biologically relevant in Yersinia infections.
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| 3. |
- Francis, Matthew S, et al.
(author)
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Regulation of type III secretion systems
- 2002
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In: Current Opinion in Microbiology. - 1369-5274 .- 1879-0364. ; 5:2, s. 166-172
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Journal article (peer-reviewed)abstract
- Type III secretion systems are utilised by numerous Gram-negative bacteria to efficiently interact with a host. Appropriate expression of type III genes is achieved through the integration of several regulatory pathways that ultimately co-ordinate the activity of a central transcriptional activator usually belonging to the AraC family. The complex regulatory cascades allow this virulence strategy to be utilised by different bacteria even if they occupy diverse niches that define a unique set of environmental cues. Simulating the appropriate combination of signals in vitro to allow a meaningful interpretation of the type III assembly and secretion regulatory cascade remains a common goal for researchers. Pieces of the puzzle slowly emerge to provide insightful views into the complex regulatory networks that allow bacteria to assemble and utilise type III secretion to efficiently colonise a host.
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| 4. |
- Francis, Matthew S, et al.
(author)
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The type III secretion chaperone LcrH co-operates with YopD to establish a negative, regulatory loop for control of Yop synthesis in Yersinia pseudotuberculosis
- 2001
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In: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 42:4, s. 1075-1093
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Journal article (peer-reviewed)abstract
- The enteropathogen Yersinia pseudotuberculosis is a model system used to study the molecular mechanisms by which Gram-negative pathogens secrete and subsequently translocate antihost effector proteins into target eukaryotic cells by a common type III secretion system (TTSS). In this process, YopD (Yersinia outer protein D) is essential to establish regulatory control of Yop synthesis and the ensuing translocation process. YopD function depends upon the non-secreted TTSS chaperone LcrH (low-calcium response H), which is required for presecretory stabilization of YopD. However, as a new role for TTSS chaperones in virulence gene regulation has been proposed recently, we undertook a detailed analysis of LcrH. A lcrH null mutant constitutively produced Yops, even when this strain was engineered to produce wild-type levels of YopD. Furthermore, the YopD-LcrH interaction was necessary to regain the negative regulation of virulence associated genes yops). This finding was used to investigate the biological significance of several LcrH mutants with varied YopD binding potential. Mutated LcrH alleles were introduced in trans into a lcrH null mutant to assess their impact on yop regulation and the subsequent translocation of YopE, a Rho-GTPase activating protein, across the plasma membrane of eukaryotic cells. Two mutants, LcrHK20E, E30G, I31V, M99V, D136G and LcrHE30G lost all regulatory control, even though YopD binding and secretion and the subsequent translocation of YopE was indistinguishable from wild type. Moreover, these regulatory deficient mutants showed a reduced ability to bind YscY in the two-hybrid assay. Collectively, these findings confirm that LcrH plays an active role in yop regulation that might be mediated via an interaction with the Ysc secretion apparatus. This chaperone-substrate interaction presents an innovative means to establish a regulatory hierarchy in Yersinia infections. It also raises the question as to whether or not LcrH is a true chaperone involved in stabilization and secretion of YopD or a regulatory protein responsible for co-ordinating synthesis of Yersinia virulence determinants. We suggest that LcrH can exhibit both of these activities.
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| 5. |
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| 6. |
- Lloyd, Scott A, et al.
(author)
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Targeting exported substrates to the Yersinia TTSS : different functions for different signals?
- 2001
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In: Trends in Microbiology. - 0966-842X .- 1878-4380. ; 9:8, s. 367-371
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Journal article (peer-reviewed)abstract
- Many Gram-negative pathogens utilize a type III secretion system (TTSS) to inject toxins into the cytosol of eukaryotic cells. Previous studies have indicated that exported substrates are targeted to the Yersinia TTSS via the coding regions of their 5' mRNA sequences, as well as by their cognate chaperones. However, recent results from our laboratory have challenged the role of mRNA targeting signals, as we have shown that the amino termini of exported substrates are crucial for type III secretion. Here, we discuss the nature of these amino-terminal secretion signals and propose a model for the secretion of exported substrates by amino-terminal and chaperone-mediated signals. In addition, we discuss the roles of chaperones as regulators of virulence gene expression and present models suggesting that such regulation can occur independently of the delivery of their substrates to the secretion apparatus.
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| 7. |
- Olsson, Jan, et al.
(author)
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The YopD translocator of Yersinia pseudotuberculosis is a multifunctional protein comprised of discrete domains.
- 2004
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In: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 186:13, s. 4110-4123
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Journal article (peer-reviewed)abstract
- To establish an infection, Yersinia pseudotuberculosis utilizes a plasmid-encoded type III translocon to microinject several anti-host Yop effectors into the cytosol of target eukaryotic cells. YopD has been implicated in several key steps during Yop effector translocation, including maintenance of yop regulatory control and pore formation in the target cell membrane through which effectors traverse. These functions are mediated, in part, by an interaction with the cognate chaperone, LcrH. To gain insight into the complex molecular mechanisms of YopD function, we performed a systematic mutagenesis study to search for discrete functional domains. We highlighted amino acids beyond the first three N-terminal residues that are dispensable for YopD secretion and confirmed that an interaction between YopD and LcrH is essential for maintenance of yop regulatory control. In addition, discrete domains within YopD that are essential for both pore formation and translocation of Yop effectors were identified. Significantly, other domains were found to be important for effector microinjection but not for pore formation. Therefore, YopD is clearly essential for several discrete steps during efficient Yop effector translocation. Recognition of this modular YopD domain structure provides important insights into the function of YopD.
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| 8. |
- Pallen, Mark J, et al.
(author)
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Tetratricopeptide-like repeats in type-III-secretion chaperones and regulators
- 2003
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In: FEMS Microbiology Letters. - 0378-1097 .- 1574-6968. ; 223:1, s. 53-60
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Journal article (peer-reviewed)abstract
- Efficient type-III secretion depends on cytosolic molecular chaperones, which bind specifically to the translocators and effectors. In the past there has been a tendency to shoe-horn all type-III-secretion chaperones into a single structural and functional class. However, we have shown that the LcrH/SycD-like chaperones consist of three central tetratricopeptide-like repeats that are predicted to fold into an all-alpha-helical array that is quite distinct from the known structure of the SycE class of chaperones. Furthermore, we predict that this array creates a peptide-binding groove that is utterly different from the helix-binding groove in SycE. We present a homology model of LcrH/SycD that is consistent with existing mutagenesis data. We also report the existence of tetratricopeptide-like repeats in regulators of type-III secretion, such as HilA from Salmonella enterica and HrpB from Ralstonia solanacearum. The discovery of tetratricopeptide-like repeats in type-III-secretion regulators and chaperones provides a new conceptual framework for structural and mutagenesis studies and signals a potential unification of prokaryotic and eukaryotic chaperone biology.
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| 9. |
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