Current Issues in Molecular Biology

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Control of Ribosome Synthesis During the Cell Division Cycles of E. coli and Synechococcus

by Yukio Asato

Curr. Issues Mol. Biol. 2005, 7(1), 109-118; https://doi.org/10.21775/cimb.007.109 - 08 Dec 2004

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The regulation of ribosome synthesis has been investigated for nearly five decades. In earlier studies, the control of rRNA synthesis in bacteria was found to be dependent on nutrient composition of the growth media or cell growth rates, and these observations led to [...] Read more.

The regulation of ribosome synthesis has been investigated for nearly five decades. In earlier studies, the control of rRNA synthesis in bacteria was found to be dependent on nutrient composition of the growth media or cell growth rates, and these observations led to the growth rate-dependent regulation model. Also developed were stringent control, feedback ribosome synthesis, passive regulation, and antitermination models. Current evidence indicates that upstream (UP) element, molecular effectors, ppGpp and iNTP (initiating nucleoside triphosphate), and trans-acting proteins, Fis and H-NS, play important roles in the control of rRNA synthesis in response to changing nutritional environments. The mechanisms for the ribosome feedback regulation, and growth rate-dependent controls of rRNA synthesis remain to be determined despite numerous investigations. r-protein synthesis can be controlled by translational coupling, translation repression, or premature transcription termination. In Synechococcus, a photoautotroph, ribosome synthesis occurs early in the cell cycle as programmed events under conditions that support balanced growth. Periods of r-protein synthesis occur before rRNA synthesis periods, and rRNA synthesis is stimulated by a light-activated gene regulatory protein. These observations suggest that gene regulatory proteins are involved in the coordinate regulation of ribosome assembly in Synechococcus. Full article

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Responses of Cariogenic Streptococci to Environmental Stresses

by José A. C. Lemos, Jacqueline Abranches and Robert A. Burne

Curr. Issues Mol. Biol. 2005, 7(1), 95-108; https://doi.org/10.21775/cimb.007.095 - 08 Dec 2004

Cited by 3 | Viewed by 836

Abstract

To persist in the oral cavity, bacteria must be able to tolerate rapid and substantial environmental fluctuations, particularly in pH and nutrient source and availability. Various species of Streptococcus, one of the most abundant genera in the mouth, are associated with oral [...] Read more.

To persist in the oral cavity, bacteria must be able to tolerate rapid and substantial environmental fluctuations, particularly in pH and nutrient source and availability. Various species of Streptococcus, one of the most abundant genera in the mouth, are associated with oral health, as well as with dental caries. Cariogenic streptococci depend on a biofilm lifestyle for survival and persistence in the oral cavity and have developed sophisticated mechanisms to cope with environmental stresses. Here, we analyze the primary factors that allow these bacteria to emerge as significant members of tooth biofilms during adverse conditions. Our focus is on the molecular mechanisms of biofilm formation, stress tolerance and sugar metabolism by pathogenic oral streptococci, mainly Streptococcus mutans. Overlaps in the roles and regulation of these virulence attributes are highlighted and areas of research that deserve further investigation are proposed. Full article

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The Surface of the Plasmodium falciparum-infected Erythrocyte

by Joseph D. Smith and Alister G. Craig

Curr. Issues Mol. Biol. 2005, 7(1), 81-94; https://doi.org/10.21775/cimb.007.081 - 08 Dec 2004

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Abstract

In order to navigate its complex lifecycle, the malaria parasites must interact with a range of host cells. Examples of this are the invasion of hepatocytes by sporozoites and erythrocyte invasion by merozoites. This requirement for cell recognition brings with it the need [...] Read more.

In order to navigate its complex lifecycle, the malaria parasites must interact with a range of host cells. Examples of this are the invasion of hepatocytes by sporozoites and erythrocyte invasion by merozoites. This requirement for cell recognition brings with it the need to display cognate ligands on the parasite surface, and therefore the capacity of the host to develop defences against the infection. Even at a stage where the intracellular nature of erythrocyte development would appear to offer an opportunity for the parasite to be immunologically "silent", parasite-derived proteins are found on the surface of the infected erythrocyte. This review will discuss the proteins found on or associated with the surface of the infected erythrocyte and the resulting phenotypes. Full article

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The Apicoplast: A Review of the Derived Plastid of Apicomplexan Parasites

by Ross F. Waller and Geoffrey I. McFadden

Curr. Issues Mol. Biol. 2005, 7(1), 57-80; https://doi.org/10.21775/cimb.007.057 - 08 Dec 2004

Cited by 155 | Viewed by 676

Abstract

The apicoplast is a plastid organelle, homologous to chloroplasts of plants, that is found in apicomplexan parasites such as the causative agents of Malaria Plasmodium spp. It occurs throughout the Apicomplexa and is an ancient feature of this group acquired by the process [...] Read more.

The apicoplast is a plastid organelle, homologous to chloroplasts of plants, that is found in apicomplexan parasites such as the causative agents of Malaria Plasmodium spp. It occurs throughout the Apicomplexa and is an ancient feature of this group acquired by the process of endosymbiosis. Like plant chloroplasts, apicoplasts are semi-autonomous with their own genome and expression machinery. In addition, apicoplasts import numerous proteins encoded by nuclear genes. These nuclear genes largely derive from the endosymbiont through a process of intracellular gene relocation. The exact role of a plastid in parasites is uncertain but early clues indicate synthesis of lipids, heme and isoprenoids as possibilities. The various metabolic processes of the apicoplast are potentially excellent targets for drug therapy. Full article

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Manipulating the Plasmodium Genome

by Teresa Gil Carvalho and Robert Ménard

Curr. Issues Mol. Biol. 2005, 7(1), 39-56; https://doi.org/10.21775/cimb.007.039 - 08 Dec 2004

Cited by 58 | Viewed by 505

Abstract

Genome manipulation, the primary tool for assigning function to sequence, will be essential for understanding Plasmodium biology and malaria pathogenesis in molecular terms. The first success in transfecting Plasmodium was reported almost ten years ago. Gene-targeting studies have since flourished, as Plasmodium is [...] Read more.

Genome manipulation, the primary tool for assigning function to sequence, will be essential for understanding Plasmodium biology and malaria pathogenesis in molecular terms. The first success in transfecting Plasmodium was reported almost ten years ago. Gene-targeting studies have since flourished, as Plasmodium is haploid and integrates DNA only by homologous recombination. These studies have shed new light on the function of many proteins, including vaccine candidates and drug resistance factors. However, many essential proteins, including those involved in parasite invasion of erythrocytes, cannot be characterized in the absence of conditional mutagenesis. Proteins also cannot be identified on a functional basis as random DNA integration has not been achieved. We overview here the ways in which the Plasmodium genome can be manipulated. We also point to the tools that should be established if our goal is to address parasite infectivity in a systematic way and to conduct refined structure-function analysis of selected products. Full article

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The Genome of Model Malaria Parasites, and Comparative Genomics

by Jane Carlton, Joana Silva and Neil Hall

Curr. Issues Mol. Biol. 2005, 7(1), 23-38; https://doi.org/10.21775/cimb.007.023 - 08 Dec 2004

Cited by 1 | Viewed by 508

Abstract

The field of comparative genomics of malaria parasites has recently come of age with the completion of the whole genome sequences of the human malaria parasite Plasmodium falciparum and a rodent malaria model, Plasmodium yoelii yoelii. With several other genome sequencing projects [...] Read more.

The field of comparative genomics of malaria parasites has recently come of age with the completion of the whole genome sequences of the human malaria parasite Plasmodium falciparum and a rodent malaria model, Plasmodium yoelii yoelii. With several other genome sequencing projects of different model and human malaria parasite species underway, comparing genomes from multiple species has necessitated the development of improved informatics tools and analyses. Results from initial comparative analyses reveal striking conservation of gene synteny between malaria species within conserved chromosome cores, in contrast to reduced homology within subtelomeric regions, in line with previous findings on a smaller scale. Genes that elicit a host immune response are frequently found to be species-specific, although a large variant multigene family is common to many rodent malaria species and Plasmodium vivax. Sequence alignment of syntenic regions from multiple species has revealed the similarity between species in coding regions to be high relative to non-coding regions, and phylogenetic footprinting studies promise to reveal conserved motifs in the latter. Comparison of non-synonymous substitution rates between orthologous genes is proving a powerful technique for identifying genes under selection pressure, and may be useful for vaccine design. This is a stimulating time for comparative genomics of model and human malaria parasites, which promises to produce useful results for the development of antimalarial drugs and vaccines. Full article

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What Do Proton Motive Force Driven Multidrug Resistance Transporters Have in Common?

by Piotr Mazurkiewicz, Arnold J.M. Driessen and Wil N. Konings

Curr. Issues Mol. Biol. 2005, 7(1), 7-22; https://doi.org/10.21775/cimb.007.007 - 08 Dec 2004

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Abstract

The extensive progress of genome sequencing projects in recent years has demonstrated that multidrug resistance (MDR) transporters are widely spread among all domains of life. This indicates that they play crucial roles in the survival of organisms. Moreover, antibiotic and chemotherapeutic treatments have [...] Read more.

The extensive progress of genome sequencing projects in recent years has demonstrated that multidrug resistance (MDR) transporters are widely spread among all domains of life. This indicates that they play crucial roles in the survival of organisms. Moreover, antibiotic and chemotherapeutic treatments have revealed that microorganisms and cancer cells may use MDR transporters to fight the cytotoxic action of drugs. Currently, several MDR extrusion systems are being investigated in detail. It is expected that understanding of the molecular basis of multidrug recognition and the transport mechanisms will allow a more rational design of new drugs which either will not be recognized and expelled by or will efficiently inhibit the activity of the MDR transporters. MDR transporters either utilize ATP hydrolysis or an ion motive force as an energy source to drive drugs out of the cell. This review summarizes the recent progress in the field of bacterial proton motive force driven MDR transporters. Full article

628 KiB

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RNA Interference: Past, Present and Future

by Tessa N. Campbell and Francis Y.M. Choy

Curr. Issues Mol. Biol. 2005, 7(1), 1-6; https://doi.org/10.21775/cimb.007.001 - 08 Dec 2004

Cited by 1 | Viewed by 697

Abstract

RNA interference (RNAi) is the sequence-specific gene silencing induced by double-stranded RNA. RNAi is mediated by 21-23 nucleotide small interfering RNAs (siRNAs) which are produced from long double-stranded RNAs by RNAse II-like enzyme Dicer. The resulting siRNAs are incorporated into a RNA-induced silencing [...] Read more.

RNA interference (RNAi) is the sequence-specific gene silencing induced by double-stranded RNA. RNAi is mediated by 21-23 nucleotide small interfering RNAs (siRNAs) which are produced from long double-stranded RNAs by RNAse II-like enzyme Dicer. The resulting siRNAs are incorporated into a RNA-induced silencing complex (RISC) that targets and cleaves mRNA complementary to the siRNAs. Since its inception in 1998, RNAi has been demonstrated in organisms ranging from trypanosomes to nematodes to vertebrates. Potential uses already in progress include the examination of specific gene function in living systems, the development of anti-viral and anti-cancer therapies, and genome-wide screens. In this review, we discuss the landmark discoveries that established the contextual framework leading up to our current understanding of RNAi. We also provide an overview of current developments and future applications. Full article

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Curr. Issues Mol. Biol., Volume 7, Issue 1 (January 2005) – 8 articles

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