bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunogenicity: Role of dendritic cells
Authors: Steinman Ralph , Inaba Kayo 
Published: February 2005

AbstractIn the development of the immune response, the dendritic cell subset of leukocytes plays a key role in enhancing immunogenicity. Dendritic cells can pick up antigens in the tissues and move to lymphoid organs, through which T cells continually recirculate. It is proposed that dendritic cells at these sites express functions which have beenidentified in tissue culture models. These involve efficient binding to antigen‐specific T lymphocytes, as well as the induction of the lymphokines and growth factor receptors required for immunity. The dendritic cell system, apparently under the control of cytokines, is a sentinel designed to signal T cells that a significant antigen burden is present, and to generate the activated T lymphoblasts that interact with many other cell types to bring about an immune response.
Dna → DNA, and DNA → RNA → protein: Orchestration by a single complex operon
Authors: Lupski James R. , Nigel Godson G. 
Published: February 2005

AbstractIn Escherichia coli, the workhorse of molecular biology, a single operon is involved in the replication, transcription and translation of genetic information. This operon is controlled in a complex manner involving multiple cis‐acting regulatory sequences and trans‐acting regulatory proteins. It interacts with global regulatory networks by mechanisms which are presently being dissected.
Re‐expression of major histocompatibility complex (UMHC) class I molecules on malignant tumor cells and its effect on host‐tumor interaction
Authors: Hui Kam M. 
Published: February 2005

AbstractThe expression of products encoded by the major histocompatibility complex (MHC) on tumor cells has recently been studied extensively. It has been found that many malignant tumor cells have their MHC antigens ‘switched‐off’ but that these antigens are re‐expressed following DNA‐mediated gene transfer, with increased tumor immunogenicity as a result and the consequence that these ‘transformed’ tumor cells are rejected in vivo.: This review will discuss approaches that have been taken to induce strong tumor‐specific immunity by the manipulation of MHC expression on tumor cells.
Modulation of gene expression by auxin
Authors: Key Joe L. 
Published: February 2005

AbstractAuxin, a class of plant hormones which affects a wide array of growth and developmental processes including cell elongation and cell division, alters gene expression in a very rapid, selective, and dramatic way. The relative level of some mRNAs decreases several fold, while that of other mRNAs increases many fold. These changes are mediated, at least in some cases, by very fast (within 5–10 min) modulation by auxin of transcription as measured by run‐off transcription assays using nuclei isolated from control and auxin‐treated tissues. Rapid turnover of mRNAs following auxin treatment also contributes to large changes in steady state concentration in some cases. The data are suggestive of multiple and complex mechanisms of regulation of expression of those genes which have been studied, using cloned cDNAs for direct quantitation of mRNA steady state levels and relative transcription rates. While there is no definitive evidence that auxin‐regulated gene expression mediates any of the growth responses effected by auxin, several lines of evidence are supportive of a very close relationship between these processes. The working hypothesis is that there is a causal relationship between the effects of auxin on gene expression and at least some of the physiological and growth responses to auxin.
The molecular genetics of early neurogenesis in Drosophila melanogaster
Authors: Knust Elisabeth , Campos‐Ortega José A. 
Published: February 2005

AbstractThe extent of neurogenesis in Drosophila is under the control of the so‐called neurogenic genes, named for their mutant phenotype of causing neural hyperplasia. Their wild‐type products appear to be responsible for a signal chain that decides the fate of ectodermal cells in the embryo. Various kinds of data, from cell transplantation experiments as well as from genetic and molecular analyses, suggest that the proteins encoded by the genes Notch and Delta may act at the membrane of the signal‐transmitting cells to provide a ligand to a still unknown receptor molecule; in contrast, the locus of Enhancer of split codes for several functions related to the transduction and further processing of the signal.
What is the role of the Cys‐his motif in retroviral nucleocapsid (NC) proteins?
Authors: Katz Richard A. , Jentoft Joyce E. 
Published: February 2005

AbstractRetroviruses encode a small, basic nucleocapsid (NC) protein that is found complexed to genomic RNA within the viral particle. The NC protein appears to function not only in a histone‐like manner in packaging the RNA into the particle but also in specifically selecting the viral genomic RNA for packaging. A cysteine‐histidine (cys‐his) region, usually composed of 14 amino acids and reminiscent of the ‘zinc fingers’ of transcription factors, is the only highly conserved sequence element among the retroviral NC proteins. This review discusses the biochemical properties of NC, and its possible role(s) in retroviral replication. We also speculate on how the biochemical properties may relate to its function in RNA recognition and packaging.
Chromosome structure at interfaces between major chromatin types: Alpha‐ and Beta‐heterochromatin
Authors: Miklos George L. Gabor , Cotsell James N. 
Published: February 2005

AbstractThe chromocenter of Drosophila polytene chromosomes, which consists of two major chromatin types, has long been a troublesome region in molecular terms. The recent microcloning of part of this region, the isolation of a monoclonal antibody to a beta‐heterochromatin binding protein, and new in situ studies now shed a little more light on this chromosomal region.
Challenges: Characterisation of engineered proteins: Some critical reflections
Authors: Dittmer Kurt E. J. , Woolley Paul 
Published: February 2005

AbstractThis essay is an attempt to point up the gap between, on the one hand, the methods currently available to the biologist in the laboratory and, on the other, the kind of data that he or she would need in order to characterise genetically engineered proteins of topical biological interest in such a way as to make use of the techniques of protein engineering.
DNA topoisomerase dysfunction: A new goal for antitumor chemotherapy
Authors: Smith Paul J. 
Published: February 2005

AbstractTopoisomerase enzymes – found in prokaryotes to human cells – control conformational changes in DNA and aid the orderly progression of DNA replication, gene transcription and the separation of daughter chromosomes at cell division. Several classes of anti‐cancer drugs are now recognised as topoisomerase poisons because of their ability to trap topoisomerase molecules on DNA as ‘cleavable complexes’. Understanding how drugs generate such complexes and why they are toxic to actively growing cancer cells is a major challenge for the development of modern approaches to chemotherapy.
Glycoconjugate expression during embryogenesis and its biological significance
Authors: Fenderson Bruce A. , Eddy E. M. , Hakomori Sen‐Itiroh 
Published: February 2005

AbstractMany stage‐specific embryonic antigens (SSEAs) have been identified as glycoconjugates. These molecules may play diverse roles in the development of the embryo, including regulation of cell growth, recognition, and differentiation. The example of SSEA‐1 is described in detail. This molecule appears to play an essential role in compaction of the early mouse embryo, and may illustrate the general importance of carbohydrate‐carbohydrate interactions in controlling cell surface interactions in development.
Topogenesis of peroxisomal proteins
Authors: Osumi Takashi , Fujiki Yukio 
Published: February 2005

AbstractMolecular and biochemical analysis of the biogenesis of peroxisomes has made rapid progress in recent years. Research on the mechanism of targeting of peroxisomal proteins has revealed that many, but not all, peroxisomal proteins have a conserved tripeptide motif in their carboxy‐terminal portions which is required for entry into peroxisomes; the topogenic signal mechanism thus differs in these instances from those employed in mitochondria and endoplasmic reticulum. Other factors involved in peroxisome biogenesis are also coming to light.
DNA polymerase delta: A second eukaryotic DNA replicase
Authors: Downey Kathleen M. , Tan Cheng‐Keat , So Antero G. 
Published: February 2005

AbstractDuring the past few years significant progress has been made in our understanding of the structure and function of the proteins involved in eukaryotic DNA replication. Data from several laboratories suggest that, in contrast to prokaryotic DNA replication, two distinct DNA polymerases are required for eukaryotic DNA replication, i.e. DNA polymerase delta for the synthesis of the leading strand and DNA polymerase alpha for the lagging strand. Several accessory proteins analogous to prokaryotic replication factors have been identified and some of these are specific for pol delta whereas others affect both DNA replicases. The replicases and their accessory proteins appear to be highly conserved in eukaryotes, as homologous proteins have been found in species ranging from humans to yeast.
Structure and function of the nuclear pore complex: New perspectives
Authors: Starr Christopher M. , Hanover John A. 
Published: February 2005

AbstractThe double membrane of the nuclear envelope is a formidable barrier separating the nucleus and cytoplasm of eukaryotic cells. However, movement of specific macromolecules across the nuclear envelope is critical for embryonic development, cell growth and differentiation. Transfer of molecules between the nucleus and cytoplasm occurs through the aqueous channel formed by the nuclear pore complex (NPC)Abbreviations: NPC, nuclear pore complex; GlcNac, N‐acetylglucosamine; WGA, wheat germ agglutinin
. Although small molecules may simply diffuse across the NPC, transport of large proteins and RNA requires specific transport signals and is energy dependent. A family of pore glycoproteins modified by O‐linked N‐acetylglucosamine moieties are essential for transport through the NPC. Recent evidence suggests that the regulation of nuclear transport may also involve the inteaction of RNA and nuclear proteins with specific binding proteins that recognize these transport signals. Are these nuclear pore glycoproteins and signal binding proteins the ‘gatekeepers’ that control access to the genetic material? Recent evidence obtained from a combination of biochemical and genetic approaches suggests – perhaps.
From cell membrane to nucleotides: The phosphate regulon in Escherichia coli
Authors: Torriani Annamaria 
Published: February 2005

AbstractMost of the essential cellular components, like nucleic acids, lipids and sugars, are phosphorylated. The phosphate equilibrium in Escherichia coli is regulated by the phosphate (Pi) input from the surrounding medium. Some 90 proteins are synthesized at an increased rate during Pi starvation and the global control of the cellular metabolism requires cross‐talk with other regulatory mechanisms. Since the Pi concentration is normally low in E. coli's natural habitat, these cells have devised a mechanism for synthesis of about 15 proteins to accomplish two specific functions: transport of Pi and its intracellular regulation. The synthesis of these proteins is controlled by two genes (the phoB‐phoR operon), involving both negative and positive functions. PhoR protein is a histidine protein kinase, induced in Pi starvation and is a transmembrane protein. It phosphorylates the regulator protein PhoB which is also Pi starvation‐induced. The PhoB phosphorylated form binds specifically to a DNA sequence of 18 nucleotides (the pho Box), which is part of the promoters of the Pho genes. The genes controlled by phoB constitute the Pho regulon.The repression of phoA (the gene encoding alkaline phosphatase) by high Pi concentrations in the medium requires the presence of an intact Pst operon (pstS, pstC, pstA, pstB and phoU) and phoR. The products of pstA and pstC are membrane bound, whereas the product of pstS is periplasmic and PstB and PhoU proteins are cytoplasmic. The function of the PhoU protein may be regulated by cofactor nucleotides and may be involved in signaling the activation of the regulon via PhoR.
Transvection and long‐distance gene regulation
Authors: Pirrotta Vincenzo 
Published: February 2005

AbstractNumerous genes contain regulatory elements located many tens of kilobases away from the promoter they control. Specific mechanisms must be required to ensure that such distant elements can find and interact with their proper targets but not with extraneous genes. This review explores the connections between transvection phenomena, the activation of domains of homeotic gene expression, position effect variegation and silencers. These various examples of long‐distance effects suggest that, in all cases, related forms of chromatin packaging may be involved.
Cholinesterases preceding major tracts in vertebrate neurogenesis
Authors: Layer Paul G. 
Published: February 2005

AbstractThe role of acetylcholinesterase (AChE) in neuro‐transmission in well known. But long before synapses are formed in vertebrates, AChE is expressed in young postmitotic neuroblasts that are about to extend the first long tracts. AChE histochemistry can thus be used to map primary steps of brain differentiation. Preceding and possibly inducing AChE in avian brains, the closely related butyrylcholinesterase (BChE) spatially fore‐shadows AChE‐positive cell areas and the course of their axons. In particular, before spinal motor axons grow, their corresponding rostral sclerotomes and myotomes express BChE, and both their neuronal source and myotomal target cells express AChE. Since axon growth has been found inhibited by acetylcholine, it is postulated that both cholinesterases can attract neurite growth cones by neutralizing the inhibitor. Thus, the early expression of both cholinesterases that is at least partially independent from classical cholinergic synaptogenesis, sheds new light on the developmental and medical significance of these enzymes.
Two‐way signalling through the Lfa‐1 lymphocyte adhesion receptor
Authors: Dustin Michael L. 
Published: February 2005

AbstractT lymphocyte recognition of foreign antigens and migration throughout the body require the regulated adhesion of lymphocytes to diverse types of cells and to the extracellular matrix. The lymphocyte adhesion ‘receptor’ LFA‐1, a member of the integrin family, interacts with ICAM‐1 and other counter‐receptors to mediate adhesion. The LFA‐1/ICAM‐1 interaction is regulated by signals transmitted from the cytoplasm to the extracellular space. Conversely, LFA‐1 transmits signals from the extracellular space to the cytoplasm to regulate T lymphocyte activation. The observed properties of LFA‐1 and related adhesion ‘receptors’ are incorporated into a general model for adhesion during immune surveillance and recognition of foreign antigens.
Targeting of proteins into the eukaryotic secretory pathway: Signal peptide structure/function relationships
Authors: Nothwehr Steven F. , Gordon Jeffrey I. 
Published: February 2005

AbstractMuch progress has been made in recent years regarding the mechanisms of targeting of secretory proteins to, and across, the endoplasmic reticulum (ER) membrane. Many of the cellular components involved in mediating translocation across this bilayer have been identified and characterized. Polypeptide domains of secretory proteins, termed signal peptides, have been shown to be necessary, and in most cases sufficient, for entry of preproteins into the lumen of the ER. These NH2‐ terminal segments appear to serve multiple roles in targeting and translocation. The structural features which mediate their multiple functions are currently the subject of intense study.
Problems And Paradigms: Golgi complex beads and the transition region
Authors: Locke Michael 
Published: February 2005

AbstractSecretory proteins and membranes move in transfer vesicles from the rough endoplasmic reticulum through the transitional region to the outer saccule of the Golgi complex. In both arthropod and vertebrate cells, the GC beads are a characteristic structural component of the transitional region. The beads are particles about half the size of ribosomes arranged equidistantly from one another and the smooth face of the ER. In an active GC, the beads are in rings through which the ER membrane emerges to form transfer vesicles. The beads may be part of the energy‐dependent step required for the movement of proteins along the secretory pathway, since they lose their ring arrangement under conditions that lower cellular ATP. The beads are organizers for Golgi complexes in the sense that they are the first recognizable components of new GCs as they arise from ER. Arthropod GC beads, but not those of vertebrates, can be visualized through their reaction with bismuth in vivo and in fixed tissue. Useful paradigms for traffic between the ER and the GC need to combine structural and biochemical information. Insect fat body, with its readily resolvable bismuth‐stained beads and easily fractionated cell components may have particular value for this problem.
Baker's yeast, the new work horse in protein synthesis studies: Analyzing eukaryotic translation initiation
Authors: Linder Patrick , Prat Annik 
Published: February 2005

AbstractThe possibility of combining powerful genetic methods with biochemical analysis has made baker's yeast Saccharomyces cerevisiae the organism of choice to study the complex process of translation initiation in eukaryotes. Several new initiation factor genes and interactions between components of the translational machinery that were not predicted by current models have been revealed by genetic analysis of extragenic suppressors of translational initiation mutants. In addition, a yeast cell‐free translation system has been developed that allows in vivo phenotypes to be correlated with in vitro biochemical activities. We summarize here the current view of yeast translational initiation obtained by these approaches.
DNA polymerase epsilon: The latest member in the family of mammalian DNA polymerases
Authors: Syväoja Juhani E. 
Published: February 2005

AbstractDNA polymerase epsilon is a mammalian polymerase that has a tightly associated 3′→5′ exonuclease activity. Because of this readily detectable exonuclease activity, the enzyme has been regarded as a form of DNA polymerase delta, an enzyme which, together with DNA polymerase alpha, is in all probability required for the replication of chromosomal DNA. Recently, it was discovered that DNA polymerase epsilon is both catalytically and structurally distinct from DNA polymerase delta. The most striking difference between the two DNA polymerases is that processive DNA synthesis by DNA polymerase delta is dependent on proliferating cell nuclear antigen (PCNA), a replication factor, while DNA polymerase epsilon is inherently processive. DNA polymerase epsilon is required at least for the repair synthesis of UV‐damaged DNA. DNA polymerases are highly conserved in eukaryotic cells. Mammalian DNA polymerases alpha, delta and epsilon are counterparts of yeast DNA polymerases I, III and II, respectively. Like DNA polymerases I and III, DNA polymerase II is also essential for the viability of cells, which suggests that DNA polymerase II (and epsilon) may play a role in DNA replication.
Integrins and tumor invasion
Authors: Dedhar Shoukat 
Published: February 2005

AbstractCell–extracellular matrix interactions are important in the process of tumor cell invasion and metastasis. In particular, the interactions of tumor cells with basement membranes of tissue epithelial, as well as vascular endothelial, cells are likely to represent key steps in the metastatic process. The interactions between cells and the connective tissue matrix are mediated by a large family of cell surface receptors, the integrins, which represent multiple receptors the integrins, which represent multiple receptors for extracellular matrix and basement membrane components. Here, I review recent progress in elucidating the roles of integrins in tumor cell invasion. Altered expression of this large family of receptors on invasive tumor cells, as compared with non‐invasive cells, may represent a fundamental step in the progressive expression of the invasive phenotype.
Growth cone inhibition – an important mechanism in neural development?
Authors: Davis Jamie A. , Cook Geoffrey M. W. 
Published: February 2005

AbstractSince the growth cone was first described a century ago by Cajal, considerable effort has been directed towards understanding the mechanisms responsible for its guidance. Traditionally, attention has focussed on the role of adhesive molecules in determining neural development. Recently, it has become apparent that inhibitory interactions may play a crucial part in axonal navigation. A common feature of inhibition seen in three model systems (peripheral nerve segmentation, retinotectal mapping and CNS/PNS segregation) is a collapse of the motile structures of the growth cone. It is increasingly clear that the identification of molecular mechanisms of inhibition, as well as those of adhesion, will be of fundamental importance to understanding neural development.
Swimming against the tide: Chemotaxis in Agrobacterium
Authors: Shaw Charles H. 
Published: February 2005

AbstractChemotaxis in bacteria is an excellent model for signal transduction processes. In Agrobacterium tumefaciens, the causative agent of crown gall tumour on wounded plants, it is a vital part of the organism's biology. A chromosomally‐determined chemotaxis system causes the bacterium to be attracted into the rhizosphere by chemoattractants in plant exudates. By interfacing with this system, the multifunctional products of two Tiplasmid encoded genes, virA and virG, allow the sensing of specific wound phenolics such as acetosyringone. This attracts Ti‐plasmid harbouring A. tumefaciens to wound sites, where the higher acetosyringone concentrations lead to virA and virG‐mediated induction of the vir‐genes. The products of the induced genes, act in concert to effect transfer of the T‐DNA to the plant cell.
Assembly and intracellular transport of snRNP particles
Authors: Andersen Janet , Zieva Gary W. 
Published: February 2005

AbstractThe assembly of the major small nuclear ribonucleoprotein (snRNP)d̊ particles begins in the cytoplasm where large pools of common core proteins are preassembled in several RNA‐free intermediate particles. Newly synthesized snRNAs transiently enter the cytoplasm and complex with core particles to form pre‐snRNP particles. Subsequently, the cap structure at the 5/end of the snRNA is hypermethylated. The Resulting trimethylguanosine (TMG) cap is an integral part of the nuclear localization signal for snRNP particles and the pre‐snRNP particles are rapidly transported into the nucleus. SnRNP particles mature when snRNA‐specific proteins complex with the particles, in some cases, just before or during nuclear transport, but in most instances after the particles are in the nucleus. In addition, U6 snRNA hybridizes with U4 snRNA to form a U4/U6 snRNP in the nucleus. The transport signals are retained on the snRNP particles and proteins since existing particles and proteins enter the reformed nucleus after mitosis.