bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular mechanisms of the chromosome condensation and decondensation cycle in mammalian cells
Authors: Adlakha Ramesh C. , Rao Potu N. 
Published: February 2005

AbstractThe chromosomes undergo a condensation‐decondensation cycle within the life cycle of mammalian cells. Chromosome condensation is a complex and critical event that is necessary for the equal distribution of genetic material between the two daughter cells. Although chromosome condensation‐decondensation and segregation is mechanistically complex, it proceeds with high fidelity during the eukaryotic cell division cycle. Cell fusion studies have indicated the presence of chromosome condensation factors in mammalian cells during mitosis. If extracts from mitotic cells are injected into immature oocytes of Xenopus laevis, they induce meiotic maturation (i.e. germinal vesicle breakdown and chromosome condensation) within 2–3 hours. Recently, we showed that the maturation‐promoting activity of the mitotic cell extracts is inactivated by certain protein factors present in cells during the G1 period. The activity of the G1 factors coincides with the process of chromosome decondensation that begins at telophase and continues throughout the G1 period. These studies have revealed that the mitotic factors and the G1 factors play a pivotal role in the regulation of condensation and decondensation of chromosomes. Furthermore, our studies strongly suggest that nonhistone protein phosphorylation and dephosphorylation may mediate chromosome condensation and decondensation, respectively.
Site‐specific mutagenesis of large DNA viral genomes
Authors: Jenkins Frank J. , Roizman Bernard 
Published: February 2005

AbstractSite‐specific or target‐specific mutagenesis of viral DNA genomes, using a selectable marker system is a powerful tool for the analysis of the function of specific regions of large DNA genomes. Through these techniques the construction of vectors capable of delivering vaccines for the prevention of infectious disease in humans and animals is possible.
Cell surface receptors for picornaviruses
Authors: Colonno Richard J. 
Published: February 2005

AbstractPicornaviruses can be divided into at least six receptor families based on results of competition binding and receptor antibody studies. It has been proposed that a canyon present within the virion capsid harbors the viral attachment site for this group of viruses. Cell surface proteins involved in viral attachment have been identified for both rhinoviruses and coxsackie B viruses. Several monoclonal antibodies have been isolated which specifically block the binding of some picornaviruses.
DNA interactions with the nuclear matrix and spatial organization of replication and transcription
Authors: Razin S. V. 
Published: February 2005

AbstractAnalysis of the DNA sequence associated with the nuclear matrix has made it possible to identify several types of DNA matrix association. Permanent attachment sites are detected in both transcriptionally active and inactive nuclei. Furthermore, replication origins have been shown to be permanently attached to the nuclear matrix. In transcriptionally active nuclei, expressed genes are also associated with the nuclear matrix. Finally, a special group of attachment sites is described; these sites are believed to maintain the fixed positions of individual chromosomes in interphase nuclei.
Immune recognition of proteins: Conclusions, dilemmas and enigmas
Authors: Smith John A. , Rose George D. 
Published: February 2005

AbstractThe immune system distinguishes between two types of antigenic sites: one of these binds to immunoglobulins (IgGs) (i.e. antibodies), while the other binds to receptor molecules on T lymphocytes (i.e. the T‐cell receptors (TcRs)). The latter interaction occurs only when the antigen is presented in association with a self‐transplantation antigen, a so‐called MHC‐restriction element. This article discusses what is known about the structure of antigenic sites and their molecular interactions with antibodies, MHC‐restriction elements, and T‐lymphocyte receptors.
Exploring molecular mechanisms in chemically induced cancer: Complementation of mammalian DNA repair defects by a prokaryotic gene
Authors: Margison G. P. , Brennand J. , Ockey C. H. , O'Connor P. J. 
Published: February 2005

AbstractExposure of man to chemical agents can occur intentionally, as in the treatment of disease, or inadvertently because the environment contains a wide range of synthetic or naturally occurring chemicals. The alkylating agents are a diverse group of compounds (Fig. 1) and comprise a good example of such xenobiotics, since much is known about their occurrence, and their biological effects include carcinogenicity, mutagenicity, toxicity and teratogenicity.Exposure to potentially carcinogenic alkylating agents such as nitrosamines may occur occupationally, from cigarette smoke, from certain foodstuffs and even endogenously through the ingestion of the appropriate precursor chemicals.1 At the other extreme, the cytotoxic effects of agents such as the chloroethylating nitrosamides or mustards have been exploited in the design of certain antitumour drugs.2 The effectiveness of antitumour agents and the other, mostly adverse, biological effects of alkylating agents have been ascribed to their ability to damage cellular macromolecules, in particular DNA. This review concentrates on investigations carried out over the past two years on the role of DNA damage in carcinogenesis, but we shall see how recent advances in this area of research have also led to a better understanding of the mechanisms of the cytotoxic effects of alkylating antitumour agents.
Diversification and progression of malignant tumors
Authors: Nicolson Garth L. , Rosenberg Nancy L. 
Published: February 2005

AbstractTumor‐cell diversification mechanisms insure that malignant neoplasms contain diversified tumor‐cell subpopulations. Because of the instability of tumor cell phenotypes, some malignant cells will evolve with the most favorable properties for their progression to highly metastatic cells. The rates of cellular phenotypic diversification vary greatly among different tumors, and they are probably modulated, in part, by genetic and chromosome defects and by epigenetic events that may vary widely depending upon the nature of the tumor cells and their microenvironments. As tumor diversification and selection proceed, the most malignant cell subpopulations may eventually become dominant and gradually lose their microenvironmental responsiveness. Tumor‐cell diversification mechanisms may be similar or identical to normal, developmentally regulated diversification mechanisms that are used during embryonic cell diversification and differentiation.
Genetic origin of diversity of human cytoskeletal tropomyosins
Authors: MacLeod A. R. 
Published: February 2005

AbstractHuman fibroblasts express five tropomyosin‐like proteins, three of which have been shown to be structurally related to each other and to tropomyoins from muscle sources. These cytoskeletal tropomyosins are transcribed from three separate, non‐overlapping structural genes. However, each of these structural genes can also produce additional tropomyosin isoforms by a tissue‐specific alternative mRNA splicing mechanism.
Gene conversion, recombination nodules, and the initiation of meiotic synapsis
Authors: Carpenter Adelaide T. C. 
Published: February 2005

AbstractThe nature of the relationship between the two types of meiotic recombination outcomes, exchange (crossing‐over) and simple gene conversion, has been debated for years. I here propose that these two types of events are not necessarily causally related and hypothesize that the primary role of events detected as simple gene conversion is in the recognition of homology during synapsis.
The structure of hepatitis B surface antigen and its antigenic sites
Authors: Peterson Darrell L. 
Published: February 2005

AbstractHepatitis B virus infects about 200 million people worldwide yearly. The consequences of the infection range from mild, self‐limiting hepatitis with full recovery and immunity to chronic infection with liver disease of varying severity, including fulminant hepatitis and death. Alternatively, individuals may become healthy carriers of the virus and thus serve as a reservoir of infection. In addition, all chronic carriers of the virus are also at risk for development of primary hepatocellular carcinoma later in life. Efforts to combat this disease on a global scale require an inexpensive vaccine. Studies of the hepatitis B viral coat protein (HBsAg) have permitted the development of two generations of vaccine to date, and detailed structural studies of its antigenic sites may eventually allow the development of a completely synthetic (and therefore inexpensive) vaccine in the future.
The yeast Ty element: Recent advances in the study of a model retro‐element
Authors: Adams Sally E. , Kingsman Susan M. , Kingsman Alan J. 
Published: February 2005

AbstractThe past three years have seen a dramatic increase in our understanding of the structural organization and expression strategies of the dispersed, repetitive yeast transposon, Ty. These studies have led to a logical comparison of Ty with retroviral proviruses and other mobile, repetitive elements. Such comparisons have culminated in the hypotheses that transposition occurs via the formation of Ty‐encoded virus‐like particles and that these particles represent a basic unit of all ‘retro‐systems’.
Protein kinases: A diverse family of related proteins
Authors: Taylor Susan S. 
Published: February 2005

AbstractHomologies in amino‐acid sequence indicate that all known protein kinases share a conserved catalytic core, and, thus, belong to a related family of proteins that have evolved in part from a common ancestoral origin. This family includes cellular kinases, oncogenic viral kinases and their protooncogene counterparts, and growth factor receptors. One of the simplest and certainly the best characterized of the protein kinases at the biochemical level is the kinase that is activated in response to cAMP. The properties of this cAMP‐dependent protein kinase are reviewed with particular emphasis on the features of nucleotide binding and catalytic mechanism that are likely to be shared by all protein kinases. In spite of this conserved catalytic core, these kinases vary widely in overall structure and in the mechanisms by which each is regulated, and these differences also are compared.
Polytene chromosomes: The status of the band–interband question
Authors: Hill Ronald J. , Rudkin George T. 
Published: February 2005

AbstractCracks in the one‐gene, one‐band paradigm for polytene chromosome organization are widening. At the same time evidence is accumulating suggesting that decondensed regions of the chromosomes (puffs, diffuse bands, interbands and possibly vacuoles within some bands) are generally associated with gene transcription. A model, now on the ascendancy, is based on the proposal that the band‐interband pattern is primarily a reflection of local transcriptional state, rather than the distribution of genic and non‐genic material.
Sodium cotransport systems: Cellular, molecular and regulatory aspects
Authors: Scott D. M. 
Published: February 2005

AbstractThe sodium cotransport systems comprise an important group of transport proteins which are involved in the transport of a variety of organic and inorganic solutes across the cellular membrane of animal cells. These systems play a central role in a wide variety of cellular and biochemical processes. We summarize here the current state of knowledge regarding the variety, structure and regulation of this important group of membrane proteins.
Pharmacogenetics of methyl conjugation and thiopurine drug toxicity
Authors: Weinshilboum Richard 
Published: February 2005

AbstractPharmacogenetics is the study of inherited variations in drug response Pharmacogenetics uses the techniques of pharmacology, population genetics, biochemical genetics and, most recently, molecular biology, to study the biological basis for individual variation in therapeutic response and in the occurrence of adverse reactions to medications. Most pharmacogenetic experiments deal with inherited differences in drug metabolism. The discussion here will review inherited variation in the activity of thiopurine methyltransferase, an enzyme that catalyzes the methyl conjugation of an important group of drugs, the thiopurines.
Composition and expression of spectrin‐based membrane skeletons in non‐erythroid cells
Authors: Moon Randall T. , McMahon Andrew P. 
Published: February 2005

AbstractCellular differentiation is often accompanied by the expression of specialized plasma membrane proteins which accumulate in discrete regions. The biogenesis of these specialized membrane domains involves the assembly and co‐localisation of a spectrin‐based membrane skeleton. While the constituents of the membrane skeleton in non‐erythroid cells are often immunologically related to erythroid spectrin, ankyrin, and protein 4.1, there are structural and functional differences between the isoforms of these membrane skeleton polypeptides, as well as highly variable patterns of expression during cellular differentiation. We consider this heterogeneity of structure and expression during development in the context of the hypothesis that non‐erythroid spectrin, ankyrin, and protein 4.1 are involved in the formation of specialized membrane domains.
Gelsolin: Calcium‐ and polyphosphoinositide‐regulated actin‐ modulating protein
Authors: Yin H. L. 
Published: February 2005

AbstractReceptor‐mediated stimulation induces massive actin polymerization and cyto‐skeletal reorganization. The activity of a potent actin‐modulating protein, gelsolin, is regulated both by Ca2+ and polyphos‐phoinositides, and it may have a pivotal role in restructuring the actin cytoskeleton in response to agonist stimulation. Structure‐function analysis of gelsolin has (1) indicated that its NH2‐terminal half is primarily responsible for modulating actin filament length and polymerization; and (2) elucidated mechanisms by which Ca2+ and phospholipids may regulate such functions. Gelsolin is functionally and structurally similar to villin, another Ca2+‐activated actin‐severing protein found in microvilli, suggesting that gelsolin may be a prototype of this family of actin‐modulating proteins. A molecular variant of gelsolin is secreted and may be involved in the clearance of actin filaments released during tissue damage. The two forms of gelsolin are encoded by a single gene, and distinct messages are derived by alternative message splicing.
The phenomenological study of the assembly of muscle and non‐muscle actin; A history in Japan
Authors: Oosawa Fumio 
Published: February 2005

AbstractThis is a brief historical view, based on my personal experience, of the phenomenological study of the assembly of actin in Japan. The morphogenesis and dynamics of protein filaments and cytoskeleton now represent one of the central problems in cell biology. The approach to this problem at the molecular level was first undertaken on actin from muscle.
Where may reaction–diffusion mechanisms be operating in metameric patterning of Drosophila embryos?
Authors: Harrison Lionel G. , Tan Karen Y. 
Published: February 2005

AbstractTwo general features of metameric patterning in Drosophilaare considered: (1) maintenance of a constant number of metameres (segments or parasegments) in the face of variation in length of the embryo; (2) expression of pattern by on‐off switchings of particular genes, with only three or four rows of cells to each element of pattern. For each of these features, the general strategic question is raised: could reaction‐diffusion theory account for this? In both cases, it is answered affirmatively. For the second feature, this review contains some hitherto unpublished computer simulations by one of us (K. Y. T.), illustrating that a reaction‐diffusion mechanism can be transformed into a patterned switching mechanism by nothing more than compartmenting of the diffusion region. For the scale of three compartments to one pattern repeat unit (representing three rows of cells to a segment) the switching pattern predicted by computation is two‐off to one‐on. This resembles the pattern of expression of the engrailed gene, posteriorly localized in each segment.
Translational regulation in sea urchin eggs: A complex interaction of biochemical and physiological regulatory mechanisms
Authors: Winkler Matthew 
Published: February 2005

AbstractThe unfertilized sea urchin egg is a metabolically quiescent cell. Fertilization results in the activation of a variety of metabolic and biosynthetic pathways, including a 20‐ to 40‐fold increase in the rate of protein synthesis by 2 h after fertilization. This increase is regulated at a purely translational level without the need for new transcription. The greatest part of this increase is due to the translation of stored maternal mRNAs which were not translated in the egg. There is also a 2‐to 3‐fold increase in the peptide elongation rate. The molecular and physiological mechanisms responsible for this activation process are beginning to be understood, and turn out to be much more complex than was anticipated.
The pathogenesis of maturity‐onset diabetes mellitus: Is there a link to islet amyloid polypeptide?
Authors: Westermark Per , Johnson Kenneth H. 
Published: February 2005

AbstractThe discovery of a novel polypeptide (Islet Amyloid Polypeptide: IAPP) isolated from human and cat islet amyloid and from amyloid of a human insulinoma is reviewed. Structurally, IAPP from the human and cat resembles calcitonin gene‐related peptide (CGRP). The structural similarities between the neuropeptide CGRP and IAPP support the premise that IAPP is hormonal in nature. Our immunohistochemical studies also indicate that normal islet B‐cells of several mammalian species (including man and cat) give strong immunoreactivity with antiserum directed to a synthetic peptide segment of IAPP. The fact that IAPP is deposited as amyloid in the pancreatic islets of type 2 (noninsulin‐dependent) diabetics strongly supports an important but yet unknown link between IAPP and the development of this disease.
Human cytogenetics: Some reminiscences
Authors: Barr Murray L. 
Published: February 2005

AbstractRoots present first‐hand accounts of discoveries in genetics, molecular biology, cellular biology, and developmental biology. In the following article, Murray L. Barr describes the background to and the events surrounding the discovery of the cytogenetic evidence for inactive × chromosomes in mammals. In the accompanying article, Michael W. McBurney reviews current molecular knowledge about the inactive × and proposes a hypothesis to explain the phenomenon.
The human genome sequence: What will it do for us?
Authors: Weinberg Robert A. 
Published: February 2005

AbstractScience and Society presents discussions and commentaries on the broader implications of contemporary biological research. In an earlier article, Walter F. Bodmer presented the case for a major commitment on the part of the scientific community to the sequencing of the human genome (Bioessays 7, 41–45, July, 1987). In the following article, Robert A. Weinberg takes a critical look at the human genome project.
The ‘BN2’ gene, a regulator for the onset of chromosome condensation
Authors: Nishimoto Takeharu 
Published: February 2005

AbstractThis review deals with the condensation–decondensation cycle of chromatin. This cycle can be analysed in increasing detail because of the availability of well‐characterized temperature‐sensitive cell‐cycle mutants in which the control for condensation is aberrant at the non‐permissive temperature. DNA transfection and gene cloning techniques using one such mutant have resulted in the identification of a gene involved in the normal regulation of entry into mitosis.
Mitotic chromosome structure
Authors: Earnshaw William C. 
Published: February 2005

AbstractThe various models of chromatin fiber folding that have been proposed over the years are considered and evaluated. It is concluded that the radial loop / scaffold model is strongly supported by the available evidence, although the term ‘scaffold’ may be an unfortunate one. The scaffold is not a solid rod running the length of the chromatid but rather appears to be an aggregation of discrete anchoring complexes for the loops of the fiber. Despite support for this model, there is a need for more evidence to resolve the questions that remain.
An illustration of the use of isotopes: The biosynthesis of porphyrins
Authors: Shemin David 
Published: February 2005

AbstractIn this article, David Shemin, who is now in retirement, describes how in 1944 he ingested 66 g of 15N‐labeled glycine in order to determine the half‐life of hemoglobin and other blood proteins. The ramifications of the experiment led to the unravelling of the biosynthesis of porphyrins and the role of glycine and α‐aminolevulinic acid in heme, vitamin B12 and chlorophyll synthesis.
Homeobox genes and development of the vertebrate CNS
Authors: Wilkinson David G. 
Published: February 2005

AbstractThe discovery of homeobox genes in vertebrates may allow analysis of a basic problem in developmental neurobiology: how regional differences in CNS organization are specified during development. This view is based on the roles defined for homologous genes in Drosophila development, and is supported by studies of the patterns of homeobox gene expression in vertebrate embryos. Homeobox genes comprise a multigene family, members of which are expressed in different spatially restricted domains along the anterior‐posterior axis of the CNS. These observations are consistent with homeobox genes having roles in the positional specification of CNS organization, and experimental tests of this should be forthcoming shortly.
O‐glycosylation pathway for mucin‐type glycoproteins
Authors: Carraway Kermit L. , Hull Steven R. 
Published: February 2005

AbstractO‐glycosylation is the post‐translational process whereby carbohydrate is added to hydroxylated amino acids of proteins. The major O‐glycosylation pathway in animal cells is involved in the synthesis of oligosaccharides linked by N‐acetylgalactosamine to serine or threonine residues in ‘mucin‐type’ proteins or their analogs. In this review, we discuss the evidence for the cellular localization of the biosynthetic steps in this pathway and propose a simplified, consensus version. We also propose variations of the simple pathway to account for its heterogeneity and variability in different cell types and differentiation states.
Mutations, epimutations, and the developmental programming of the maize Suppressor‐mutator transposable element
Authors: Fedoroff Nina , Masson Patrick , Banks Jo Ann 
Published: February 2005

AbstractInformation about the structure, function and regulation of the maize Suppressormutator (Spm) transposable element has emerged from the genetic and molecular characterization of both deletion mutations and an unconventional type of reversible genetic change (epimutation). The element is subject to an epigenetic mechanism that can either stably inactivate it or specify one of a variety of heritable programs of differential element expression in development. The essay explores the relationship between the Spm element's epigenetic developmental programming mechanism and the determinative events central to plant development and differentiation.