| 1. |
- Hedlund, Maria, et al.
(författare)
-
Sphingomyelin, glycosphingolipids, and ceramide signalling in cells exposed to p-fimbriated Escherichia coli
- 1998
-
Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 29:5, s. 1297-1306
-
Forskningsöversikt (refereegranskat)abstract
- Uropathogenic Escherichia coli attach to epithelial cells through P fimbriae that bind Galα1‐4Galβ‐oligosaccharide sequences in cell surface glycosphingolipids. The binding of P‐fimbriated E. coli to uroepithelial cells causes the release of ceramide, activation of the ceramide signalling pathway and a cytokine response in the epithelial cells. The present study examined the molecular source of ceramide in human kidney A498 cells exposed to P‐fimbriated E. coli. Agonists such as TNF‐α and IL‐1β released ceramide from sphingomyelin by the activation of endogenous sphingomyelinases and hydrolysis of sphingomyelin, and triggered an IL‐6 response. P‐fimbriated E. coli caused a slight increase in endogenous sphingomyelinase activity, but there was no associated sphingomyelin hydrolysis. Instead, the concentration of galactose‐containing glycolipids decreased. We propose that P‐fimbriated E. coli differ from other activators of the ceramide pathway, in that release of ceramide is from receptor glycolipids and not from sphingomyelin. Receptor breakdown may be an efficient host defence strategy, as it reduces the concentration of cell surface receptors, releases soluble receptor analogues and activates an inflammatory response.
|
|
| 2. |
- Piskur, Jure, et al.
(författare)
-
Yeast genome sequencing: the power of comparative genomics
- 2004
-
Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 53:2, s. 381-389
-
Forskningsöversikt (refereegranskat)abstract
- For decades, unicellular yeasts have been general models to help understand the eukaryotic cell and also our own biology. Recently, over a dozen yeast genomes have been sequenced, providing the basis to resolve several complex biological questions. Analysis of the novel sequence data has shown that the minimum number of genes from each species that need to be compared to produce a reliable phylogeny is about 20. Yeast has also become an attractive model to study speciation in eukaryotes, especially to understand molecular mechanisms behind the establishment of reproductive isolation. Comparison of closely related species helps in gene annotation and to answer how many genes there really are within the genomes. Analysis of non-coding regions among closely related species has provided an example of how to determine novel gene regulatory sequences, which were previously difficult to analyse because they are short and degenerate and occupy different positions. Comparative genomics helps to understand the origin of yeasts and points out crucial molecular events in yeast evolutionary history, such as whole-genome duplication and horizontal gene transfer(s). In addition, the accumulating sequence data provide the background to use more yeast species in model studies, to combat pathogens and for efficient manipulation of industrial strains.
|
|
| 3. |
- Rasmussen, Magnus, et al.
(författare)
-
Proteolysis and its regulation at the surface of Streptococcus pyogenes.
- 2002
-
Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 43:3, s. 537-544
-
Forskningsöversikt (refereegranskat)abstract
- Pathogenic bacteria often produce proteinases that are believed to be involved in virulence. Moreover, several host defence systems depend on proteolysis, demonstrating that proteolysis and its regulation play an important role during bacterial infections. Here, we discuss how proteolytical events are regulated at the surface of Streptococcus pyogenes during infection with this important human pathogen. Streptococcus pyogenes produces proteinases, and host proteinases are produced and released as a result of the infection. Streptococcus pyogenes also recruits host proteinase inhibitors to its surface, suggesting that proteolysis is tightly regulated at the bacterial surface. We propose that the initial phase of a S. pyogenes infection is characterized by inhibition of proteolysis and complement activity at the bacterial surface. This is achieved mainly through binding of host proteinase inhibitors and complement regulatory proteins to bacterial surface proteins. In a later phase of the infection, massive proteolytic activity will release bacterial surface proteins and degrade human tissues, thus facilitating bacterial spread. These proteolytic events are regulated both temporally and spatially, and should influence virulence and the outcome of S. pyogenes infections.
|
|
| 4. |
- Andersson, Dan I., et al.
(författare)
-
Biological roles of translesion synthesis DNA polymerases in eubacteria
- 2010
-
Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 77:3, s. 540-548
-
Forskningsöversikt (refereegranskat)abstract
- Biological systems are strongly selected to maintain the integrity of their genomes by prevention and repair of external and internal DNA damages. However, some types of DNA lesions persist and might block the replication apparatus. The universal existence of specialized translesion synthesis DNA polymerases (TLS polymerases) that can bypass such lesions in DNA implies that replication blockage is a general biological problem. We suggest that the primary function for which translesion synthesis polymerases are selected is to rescue cells from replication arrest at lesions in DNA, a situation that, if not amended, is likely to cause an immediate and severe reduction in cell fitness and survival. We will argue that the mutagenesis observed during translesion synthesis is an unavoidable secondary consequence of this primary function and not, as has been suggested, an evolved mechanism to increase mutation rates in response to various stresses. Finally, we will discuss recent data on additional roles for translesion synthesis polymerases in the formation of spontaneous deletions and in transcription-coupled TLS, where the coupling of transcription to TLS is proposed to allow the rescue of the transcription machinery arrested at DNA lesions.
|
|
| 5. |
- Bernander, Rolf
(författare)
-
The cell cycle of Sulfolobus
- 2007
-
Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 66:3, s. 557-562
-
Forskningsöversikt (refereegranskat)abstract
- Much of the current information about the archaeal cell cycle has been generated through studies of the genus Sulfolobus. The overall organization of the cell cycle in these species is well understood, and information about the regulatory principles that govern cell cycle progression is rapidly accumulating. Exciting progress regarding the control and molecular details of the chromosome replication process is evident, and the first insights into the elusive crenarchaeal mitosis and cytokinesis machineries are within reach.
|
|
| 6. |
- Bouet, Jean-Yves, et al.
(författare)
-
Plasmid partition and incompatibility : the focus shifts
- 2007
-
Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 65:6, s. 1405-1414
-
Forskningsöversikt (refereegranskat)abstract
- The mitotic apparatus that a plasmid uses to ensure its stable inheritance responds to the appearance of an additional copy of the plasmid's centromere by segregating it from the pre-existing copies: if the new copy arises by replication of the plasmid the result is partition, if it arrives on a different plasmid the result is incompatibility. Incompatibility thus serves as a probe of the partition mechanism. Coupling of distinct plasmids via their shared centromeres to form mixed pairs has been the favoured explanation for centromere-based incompatibility, because it supports a long-standing assumption that pairing of plasmid replicas is a prerequisite for their partition into daughter cells. Recent results from molecular genetic and fluorescence microscopy studies challenge this mixed pairing model. Partition incompatibility is seen to result from various processes, including titration, randomized positioning and a form of mixed pairing that is based on co-activation of the same partition event rather than direct contact between partition complexes. The perspectives thus opened onto the partition mechanism confirm the continuing utility of incompatibility as an approach to understanding bacterial mitosis. The results considered are compatible with the view that direct pairing of plasmids is not essential to plasmid partition.
|
|
| 7. |
- Kirsebom, L A
(författare)
-
RNase P--a 'Scarlet Pimpernel'.
- 1995
-
Ingår i: Mol Microbiol. - : Wiley. - 0950-382X .- 1365-2958. ; 17:3, s. 411-20
-
Forskningsöversikt (populärvet., debatt m.m.)
|
|
| 8. |
- Mandin, Pierre, et al.
(författare)
-
Feeling the heat at the millennium : thermosensors playing with fire
- 2020
-
Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 113:3, s. 588-592
-
Forskningsöversikt (refereegranskat)abstract
- An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.
|
|
| 9. |
- Mattola, S., et al.
(författare)
-
Nuclear entry and egress of parvoviruses
- 2022
-
Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 118:4, s. 295-308
-
Forskningsöversikt (refereegranskat)abstract
- Parvoviruses are small non-enveloped single-stranded DNA viruses, which depend on host cell nuclear transcriptional and replication machinery. After endosomal exposure of nuclear localization sequence and a phospholipase A(2) domain on the capsid surface, and escape into the cytosol, parvovirus capsids enter the nucleus. Due to the small capsid diameter of 18-26 nm, intact capsids can potentially pass into the nucleus through nuclear pore complexes (NPCs). This might be facilitated by active nuclear import, but capsids may also follow an alternative entry pathway that includes activation of mitotic factors and local transient disruption of the nuclear envelope. The nuclear entry is followed by currently undefined events of viral genome uncoating. After genome release, viral replication compartments are initiated and infection proceeds. Parvoviral genomes replicate during cellular S phase followed by nuclear capsid assembly during virus-induced S/G2 cell cycle arrest. Nuclear egress of capsids occurs upon nuclear envelope degradation during apoptosis and cell lysis. An alternative pathway for nuclear export has been described using active transport through the NPC mediated by the chromosome region maintenance 1 protein, CRM1, which is enhanced by phosphorylation of the N-terminal domain of VP2. However, other alternative but not yet uncharacterized nuclear export pathways cannot be excluded.
|
|
| 10. |
- Moraleda-Munoz, Aurelio, et al.
(författare)
-
Metal-responsive RNA polymerase extracytoplasmic function (ECF) sigma factors
- 2019
-
Ingår i: Molecular Microbiology. - : WILEY. - 0950-382X .- 1365-2958. ; 112:2, s. 385-398
-
Forskningsöversikt (refereegranskat)abstract
- In order to survive, bacteria must adapt to multiple fluctuations in their environment, including coping with changes in metal concentrations. Many metals are essential for viability, since they act as cofactors of indispensable enzymes. But on the other hand, they are potentially toxic because they generate reactive oxygen species or displace other metals from proteins, turning them inactive. This dual effect of metals forces cells to maintain homeostasis using a variety of systems to import and export them. These systems are usually inducible, and their expression is regulated by metal sensors and signal-transduction mechanisms, one of which is mediated by extracytoplasmic function (ECF) sigma factors. In this review, we have focused on the metal-responsive ECF sigma factors, several of which are activated by iron depletion (FecI, FpvI and PvdS), while others are activated by excess of metals such as nickel and cobalt (CnrH), copper (CarQ and CorE) or cadmium and zinc (CorE2). We focus particularly on their physiological roles, mechanisms of action and signal transduction pathways.
|
|
