bluuebunny/crossref_metadata_2025 huggingface dataset:
What the papers say: Trisphosphoinositol as the intra‐myonal signal messenger, crucial in excitation‐contraction coupling in muscle
Authors: Mommaerts W. F. H. M.
Published: February 2005

Evidence is reviewed here that inositol (1, 4, 5) trisphosphate (Ins P3) is a key signal in translating the electrophysiological event in muscle stimulation into the molecular‐mechanical events of contraction. Not least, these findings raise questions about the suitability of the term ‘second messenger’.
Catalysis by RNA
Authors: Waugh David S. , Pace Norman R.
Published: February 2005

Until the discovery of catalytic RNA, the notion that all enzymes are proteins had seemed incontrovertible. Now the existence of RNA enzymes has been confirmed in a variety of contexts. What is known about the chemistry of RNA‐catalyzed reactions is reviewed below, with particular attention to the self‐splicing rRNA intron of Tetrahymena thermophila and the processing of pre‐tRNA molecules by RNase P.
Human choriogonadotropin
Authors: Puett David
Published: February 2005

Human choriogonadotropin, a hormone derived from the syncytiotrophoblast cells of the placenta, is a member of the glycoprotein hormone family which also contains the pituitary hormones lutropin, follitropin and thyrotropin. These four hormones are comprised of two dissimilar subunits, one (α) being common to all four and the other (β) conferring hormonal specificity. Information is rapidly accumulating on the nature and regulation of the genes for these subunits, as well as the structural aspects, mechanism‐of‐action and physiological roles of these complex hormones. This mini review considers some of the recent advances in our understanding of human choriogonadotropin.
Structural analysis of a yeast centromere
Authors: Bloom Kerry , Hill Alison , Yeh Elaine
Published: February 2005

The most striking region of structural differentiation of a eukaryotic chromosome is the kinetochore. This chromosomal domain plays an integral role in the stability and propagation of genetic material to the progeny cells during cell division. The DNA component of this structure, which we refer to as the centromere, has been localized to a small region of 220–250 base pairs within the chromosomes from the yeast Saccharomyces cerevisiae. The centromere DNA (CEN) is organized in a unique structure in the cell nucleus and is required for chromosome stability during both mitotic and meiotic cell cycles. The centromeres from one chromosome can stabilize small circular minichromosomes or other yeast chromosomes. The centromeres may therefore interact with the same components of the segregation apparatus regardless of the chromosome in which they reside. The CEN DNA does not encode any regulatory RNAs or proteins, but rather is a cis‐acting element that provides genetic stability to adjacent DNA sequences.
Endocytosis and epithelial biogenesis in the mouse early embryo
Authors: Fleming Tom P.
Published: February 2005

The polarized organization of epithelial cells is expressed in many ways including the morphology of the cell surface or cytocortex, the molecular composition of membrane domains and the distribution of cytoplasmic organelles. The differentiation of mouse trophectoderm is described with particular attention given to the maturation of the endocytic system in an attempt to define how the complex assembly of an epithelium may be generated.
Molecular analysis of familial human growth hormone disorders
Authors: Repaske David R. , Phillips John A.
Published: February 2005

There is a diverse group of human genetic disorders affecting growth hormone action that lead to short stature. Insights into their pathophysiology can be gained by a combination of classical and molecular genetic studies.
Cell‐surface receptors: Puzzles and paradigms
Authors: Geisow Michael J.
Published: February 2005

The determination of amino acid sequences representing the cell‐surface receptors for transferrin,1 asialoglycoprotein,2 polymeric immunoglobulin (IgA/IgM),3 epidermal growth factor (EGF),4 lowdensity lipoprotein (LDL)5 and insulin6 has produced new paradingms for receptor architecture. This review examines common features of the protiens and describes the intriguing functional and evolutionary puzzles that have arisen from them.
Cell interactions in the developing leech embryo
Authors: Bissen Shirley T. , Ho Robert K. , Weisblat David A.
Published: February 2005

The stereotyped pattern of cell commitments during leech embryogenesis is described. The nature of cell commitments during segmentation differs significantly between leech and fruit fly. Despite the constancy of cell fate assignments in normal development, ablation experiments show that cell interactions are essential in setting some of these commitments. Interacting cells follow a positionally determined hierarchy of fate choices. For other cells, which appear to have fates fixed from birth, the possibility of determinative interactions between mother and daughter cells is discussed.
Nucleosome Positioning In Vivo and In Vitro
Authors: Simpson Robert T.
Published: February 2005

Nucleosome positioning refers to sequence‐specific locations for histones interacting with the nucleic acid. Examples of occurrence of this phenomenon, its possible mechanisms and its significance are presented.
Methylation and the X chromosome
Authors: Monk Marilyn
Published: February 2005

Recent approaches towards an understanding of the molecular basis of X‐chromosome inactivation in mammals suggest that regulation is due to multiple events including DNA methylation.
What regulates secretion of non‐stored proteins by eukaryotic cells?
Authors: Gebhart Ann Marie , Ruddon Raymond W.
Published: February 2005

Protein secretion is conventionally viewed as taking place by either of two cellular routes, a regulated pathway, involving external stimuli and secretory granules, and a presumptive ‘constitutive’ pathway, which does not involve hormonal or neuronal stimuli or the production of secretory granules. The evidence reviewed here strongly suggests that there are post‐synthesis rate‐limiting steps for many proteins released by the ‘constitutive’ pathway and, hence, that regulation in some sense is involved here too. The nature of these rate‐limiting determinants and events is discussed.
T‐cell differentiation antigens: Proteins, genes and function
Authors: Parnes Jane R.
Published: February 2005

T‐lymphocyte recognition, activation and function involve anumber of T‐cell‐specific surface proteins in addition to the receptor for antigen. The structure, function and genetic analysis of four of these T‐cell differentiation antigens are discussed.
Pathways of human T lymphocyte development and activation
Authors: Alcover Andres , Milanese Claudio , Reinherz Ellis L.
Published: February 2005

The T lymphocyte receptor for antigen, which operates in conjunction with gene products of the major histocompatibility complex (MHC), is a molecular complex comprised of five polypeptide chains. Both the 49 kDa alpha and 43 kDa beta chains are immunoglobulin‐like and thus contain variable domains responsible for ligand binding. In contrast, the 20–25 kDa T3 gamma, delta and epsilon chains are monomorphic structures presumably involved in transmembrane signalling. The alpha and beta subunits are disulfide bonded to each other and held in noncovalent association with the T3 chains. T3‐Ti receptor crosslinking leads to conformational modification of a second T lineage specific molecule, termed the 50 kDa T11 structure which in turn leads to protein kinase C activation, elevation in intracytoplasmic free calcium and Na+/H+ antiport stimulation.
Roots: Why affinity progression of antibodies during immune responses is probably not accompanied by parallel changes in the immunoglobulin‐like antigen‐specific receptors on T cells
Authors: Eisen Herman N.
Published: February 2005

There can be no doubt that a closer study of avidity will be an indispensable step towards understanding the mechanisms of immunity. N. K. Jerne, 1951, p. 1403.
Problem and paradigms: Somatic generation of a genetic polymorphism: Towards the solution of the I‐J Enigma
Authors: Tada Tomio , Asano Yoshihiro
Published: February 2005

I‐J has been regarded as a polymorphic genetic marker controlled by a locus in the major histocompatibility complex (MHC) which is expressed only on functional T cells. However, this antigenic determinant has been found not to be directly encoded by the MHC gene per se but is somatically generated according to the MHC of the cellular environment during ontogeny. This explains the apparent linkage of I‐J to MHC, despite the failure to find the structural gene for I‐J within the MHC. The I‐J paradox provides an instance of a polymorphism that does not follow the standard genetics of Mendelian structural genes.
Growth factors, receptors and cancer
Authors: Burgess Antony W.
Published: February 2005

It now appears that the molecular events associated with the mitogenic action of growth factors are also the events perturbed in neoplastic lesions. This review outlines the relevance of our recent progress in the biochemistry of growth factors and their receptors to the induction and maintenance of the neoplastic state.
Spectrin subtypes in mammalian brain
Authors: Goodman Steven R. , Riederer Beat M. , Zagon Lan S.
Published: February 2005

Mammalian neural cells contain at least two forms of brain spectrin: brain spectrin (240/235) which is located primarily in the axons and presynaptic terminals of neurons, and brain spectrin (240/235E) which is found in the cell bodies, dendrites and postsynaptic terminals of neurones. Brain spectrin (240/235E) is also found in certain glial cell types. Antibodies against red blood cell spectrin detect only brain spectrin (240/235E), while antibodies against brain spectrin isolated from axonal and synaptic membranes detect brain spectrin (240/235). Previous apparent discrepancies in the literature concerning brain spectrin localization at the light microscope level were undoubtedly due to different laboratories detecting distinct brain spectrin subtypes, based on the particular antibody being utilized for immunohistochemistry. In this review we (1) discuss the data supporting the presence of at least two distinct subtypes of mammalian brain spectrin, (2) explain how these results reconcile previous discrepancies concerning the localization of spectrin within neural cells, and (3) suggest the future implications of these findings.
Molecular aspects of atrial natriuretic peptides
Authors: Imamura Toshiko , Miura Yoshiaki
Published: February 2005

Peptides possessing both natriuretic and smooth muscle relaxant activities have been isolated from heart atria and their structures have been determined. The peptides designated ANP (atrial natriuretic peptide) regulate salt and water balance and blood pressure. The scope of this article is to provide a summary of recent research developments directed towards understanding the molecular nature of atrial natriuretic peptides.
Single‐stranded DNA‐containing bacteriophages
Authors: Zinder Norton D.
Published: February 2005

Roots presents articles on major discoveries that laid the basis for contemporary molecular and cellular biology. In this article, Norton D. Zinder reviews the first findings about the single‐stranded DNA‐containing bacteriophages and what is known today about the genetics and molecular biology of these phages.
The amdS gene of Aspergillus nidulans: Control by multiple regulatory signals
Authors: Hynes Michael J. , Davis Meryl A.
Published: February 2005

The amdS gene of A. nidulans has proved extremely favourable for the isolation of mutations affecting gene regulation. Trans‐acting regulatory genes involved in amdS induction by small molecular weight effectors have been identified – amdR (ω‐amino acids) facB (acetate) and amdA (acetate). Another gene, the areA gene, has properties expected of a major activator gene involved in nitrogen metabolite repression of amdS. All of these regulatory genes are also involved in the control of various other functions encoded by structural genes unlinked to amdS. Mutations in the 5′‐region adjacent to amdS have been isolated and allow the identification of independent cis‐acting sequences which are the target sites for the regulatory genes. The involvement of these sequences in regulatory product binding has been deduced from titration studies using transformants containing multiple copies of the 5′ sequences. A combination of genetics and molecular analysis is allowing a detailed characterization of this system.
The replication of cowpea mosaic virus
Authors: Van Kammen A. , Eggen H. I. L.
Published: February 2005

Cowpea mosaic virus (CPMV) is the type member of the comovirus group, which contains 14 different plant viruses that have the same structural organization of genomic RNAs and virions and use the same mechanism for expression of the viral RNAs. The combined structure and organization of the two CPMV genomic RNAs is strikingly similar to that of the single genome of animal picornaviruses. This suggests a common ancestry and similar replication mechanisms. CPMV is by far the best‐studied comovirus and we shall limit this review to some recent data on this virus. For additional general information the reader is referred to other recent reviews on CPMV and comoviruses1,2.
Retinoblastoma – genetic insights into neoplasia
Authors: Nyhan William L.
Published: February 2005

Retinoblastoma is a highly malignant ocular tumor that has been known to be hereditary in some instances. New information from cytogenetic and molecular studies indicates that there is a retinoblastoma gene and that the mutant alleles are recessive. The wild‐type gene appears to be a suppressor of this neoplasia, and, when both alleles are lost, malignancy develops.
Drosophila segmentation genes and blastoderm cell identities
Authors: Gergen J. Peter
Published: February 2005

The formation of the segmentation pattern in Drosophila embryos provides an excellent model for investigating the process of pattern formation in multicellular organisms. Several genes required in an embryo for normal segmentation have been analyzed by classical and molecular genetic and morphological techniques. A detailed consideration of these results suggests that these segmentation genes are combinatorially involved in translating the positional identities of individual cells at an early stage in Drosophila development.
The lin‐12 locus of Caenorhabditis elegans
Authors: Greenwald Iva
Published: February 2005

Analysis of the patterns of cell lineage observed during development of the nematode Caenorhabditis elegans, combined with selected cell ablation experiments, has revealed that while many cell fates are autonomously (intrinsically) determined, cell–cell interactions are required for a number of developmental decisions. Earlier genetic analysis of one key gene, lin‐12, had shown that this gene controls a number of bi‐potential fate decisions involving such cellular interactions. Molecular analysis of this gene is now providing clues to its mode of action in mediating these cell‐fate decision.
Overcoming random diffusion in polarized cells – corralling the drunken beggar
Authors: Wolf David E.
Published: February 2005

Cells are capable of overcoming the randomizing effect of lateral diffusion in order to regionally differentiate their surfaces. Such local structural specializations are of major significance to cellular function. In some cases, they may be explained by diffusion rates that are insufficient to completely randomize surface gradients over biologically relevant times scales. However, in other cases, absolute and permanent regionalizations are also observed. Mechanistically, the problem is analogous to equilibrium across a dialysis bag: either an absolute barrier exists or the chemical potential between two adjacent regions must be equal. The interactive nature of the system, where localizations of one component lead to localization of others, are also considered here.
Biodegradation of environmental pollutants by the white rot fungus Phanerochaete chrysosporium: Involvement of the lignin degrading system
Authors: Bumpus John A. , Aust Steven D.
Published: February 2005

The white‐rot fungus Phanrochaete chrysosporium has the ability to degrade a wide variety of structurally diverse organic compounds, including a number of environmentally persistent organopollutants. The unique biodegradative abilities of this fungus appears to be dependent upon its lignin‐degrading system. The non‐specific and partially extracellular nature of this system suggests that it may be useful as a supplementary means to treat organochemical wastes.
Mechanisms of receptor function and the molecular biology of information processing in bacteria
Authors: Stock Jeff
Published: February 2005

Bacteria adapt to changes in their environment by altering their metabolism, turning on and off genes, and moving toward favorable conditions. Recent results indicate that a common molecular logic may underlie the decision‐making processes by which these simple cells adjust to their surroundings.
Branched RNA
Authors: Edmonds Mary
Published: February 2005

The only RNA molecules known to be branched are circular structures with tails known as lariats that arise during nuclear pre‐mRNA splicing. Lariats accumulate within a large multicomponent particle called a spliceosome that forms upon the addition of unspliced mRNA to nuclear extracts. Recently an RNA molecule has been observed to catalyze branch formation. In this case a single intron of a yeast mitochondrial pre‐mRNA participates in a self‐splicing reaction that results in the accumulation of branched lariats that are processed to correctly spliced exons.

An enzyme highly specific for branch removal found in the same extracts that form branches during pre‐mRNA splicing can debranch RNA lariats to their linear forms without loss of nucleotides.

The chemical synthesis of branched RNA has recently been achieved. High yields of sequence‐specific oligonucleotides are now available for the analysis of RNA splicing by techniques dependent on branch‐site recognition.
Sucrose transport in plants
Authors: Hitz William D. , Giaquinta Robert T.
Published: February 2005

Physiological studies show that the driving force for long distance transport and the control of nutrient movement in plants resides largely in the regulated, membrane transport of a few carbohydrates, principally sucrose. The evidence is reviewed here and biochemical studies on sucrose carrier proteins are discussed.
Regulation of messenger RNA stability in eukaryotic cells
Authors: Shapiro David J. , Blume John E. , Nielsen David A.
Published: February 2005

Regulation of the cytoplasmic stability of mRNAs has recetly been identified as a major control mechanism which governs mRNA levels in a variety of eukaryotic systems. In this review we discuss what is known about several experimental systems that exhibit regulated mRNA stability, describe the mechanisms that cells may use to achieve control of mRNA degradation, and suggest areas of future investigation likely to provide new insights into this process.
The screening of enzyme‐targeted drugs
Authors: Tsou C. L.
Published: February 2005

In this article C. L. Tsou, of the Institute of Biophysics, Beijing, criticizes the use of the expression I50, the inhibitor concentration to produce 50% inhibition of a particular enzyme as a ‘most unfortunate’ parameter, when screening enzyme inhibitors designed as drugs. Comments on Dr Tsou's point of view will be welcomed from readers.
Molecular analysis of human monogenic diseases
Authors: Davies K. E. , Robson K. J. H.
Published: February 2005

Over one hundred genes have been isolated from the human genome and shown to be causally related to specific human genetic diseases. Studies with gene‐specific probes have demonstrated that the mutations resulting in a particular phenotype are highly heterogeneous as a group, ranging from alterations in transcription or RNA processing in the nucleus, through to errors in mRNA translation in the cytoplasm. Even where the gene‐specific probe is not available, defects have been localized to chromosomal regions by family studies. Recently developed methods for moving along the chromosome from a linked marker to the mutation are resulting in rapid advances in the understanding of many monogenic disorders.
Increasing bacterial disease resistance in plants utilizing antibacterial genes from insects
Authors: Jaynes Jesse M. , Xanthopoulos Kleanthis G. , Destéfano‐Beltrán Luis , Dodds John H.
Published: February 2005

The introduction of genes into plants encoding potent antibacterial proteins, derived from insects, may significantly augment the level of their resistance to bacterial disease. Using modern techniques, genes of choice can be introduced into plant tissue and this tissue can be manipulated to produce viable plants. The potato has been chosen as the model system, not only because of its plasticity of development, which allows for the relatively easy regeneration of whole plants from transformed tissue, but also because the potato ranks among the top four plants in the world in terms of economic importance.
The origin, development and regulation of osteoclasts
Authors: Osdoby Philip , Krukowski Marilyn , Oursler Merry Jo , Salino‐Hugg Teresa
Published: February 2005

Osteoclasts, the multinucleated cells primarily responsible for dissolution of bone tissue, form by fusion of precursors that circulate in the bloodstream. A variety of factors have been shown to affect the mature osteoclast and its progenitor cell, such as calcium‐regulating hormones, products of the immune system, and constituents of the arachidonic acid cascade. To date, however, the osteoclast precursor has not been identified. Furthermore, there is limited information on the factors that influence osteoclast development and regulation, reflecting in part the paucity of data on the osteoclast cell surface. Recent progress in understanding osteoclasts formation and function is discussed.
The potential of adipokinetic hormone to teach us about neuropeptides
Authors: Schaffer Martin H. , Noyes Barbara E.
Published: February 2005

Genetic manipulation and purification techniques are facilitating research into the biology of arthropod neuropeptides. The red pigment concentrating hormone (RPCH)/ adipokinetic hormone (AKH) family are a conserved group of peptides which were first recognized for their hormonal activities. Biosynthesis of AKH in the grasshopper seems to proceed via a large protein precursor (12 kDa) in the cell body of the neuron, which implies precise coordination of synthesis and neural activity. Beginning with a 10 amino acid stretch of known precursor protein sequence, an oligonucleotide primer approach is being used to clone a recombinant AKH gene. Once achieved, this will allow fundamental questions on the biochemistry and physiology of neuropeptides to be addressed. Such work in an arthropod system raises the intriguing possibility of studying neuropeptide level and synthetic activity in single, defined neurons.
Approaching the biochemistry of virus multiplication
Authors: Cohen Seymour S.
Published: February 2005

The evolution of research on the biochemistry of virus multiplication cannot be understood without knowing something of the structure of biochemistry and of virology before, during and immediately after World War II. My own research on virus multiplication began after studies on plant viruses and wartime research on the rickettsial components of the typhus vaccine, all of which involved work on the nucleic acids. Interest in the chemotherapy of virus disease led to a search for a model system. A simple methodology for handling phage systems enabled biochemists to examine infected cells. The fortuitous use of an extremely virulent phage group (the T‐even phages) which evoke marked changes in polymeric products without affecting the production of energy and small building blocks facilitated these studies. An exaggerated synthesis of viral DNA by these phages concentrated our attention on the origins of this substance, which proved to contain a new pyrimidine deoxyribonucleotide, synthesized by a novel virus‐determined enzyme. The generality of the existence of virus‐induced enzymes and other proteins may be the key to a chemotherapy of virus infection.
Molecular mimicry of carbohydrate and protein structures by hybridoma antibodies
Authors: Olsson Lennart
Published: February 2005

A large proportion of tumour‐associated antigens seem to be determined by carbohydrate structures. Advances in the study of the antigenicity of cell‐surface carbohydrates have been hampered by the absence of advanced monoclonal hybridoma technology comparable to that available for the study of protein antigens. Monoclonal antibodies have been raised against a carbohydrate epitope (43–9F) that is associated with the proliferative features of squamous lung carcinomas. These were used in turn to generate anti‐idiotype antibodies with homology to 43–9F. The method and its possible applications are described, together with a procedure to detect rare cell membrane variants within large populations.
What are the functions of kinesin?
Authors: Sheetz Michael P.
Published: February 2005

A variety of intracellular motile processes involve the directed movement of particles along microtubules, including organelle transport, endoplasmic reticulum extension, and movements in mitosis. Recently, a microtubule‐dependent motor protein, kinesin, was purified and was found to be present in a soluble form in a wide variety of organisms and tissues. Because microtubules provide polar pathways over long distances within cells, kinesin and the motors which move in the opposite direction to kinesin on microtubules provide a mechanism for directed communications within cells. The possible roles of kinesin and other soluble microtubule‐dependent motors in intracellular motile functions are discussed in the light of recent studies of the reconstitution of organelle motility with isolated components.
Towards the genetic dissection of mitosis in Drosophila
Authors: Ripoll Pedro , Casal José , González Cayetano
Published: February 2005

Cell division is an universal process the aim of which is the equitable distribution of subcellular organelles from single cells to their daughters. The extraordinary accuracy with which the genetic material is partitioned requires a complex machinery involving many gene products. Genetic approaches can be used to identify the relevant components and processes, and mutational analysis of loci essential for cell division has been carried out in several eukaryotes, in particular fungi and mammalian cells in culture. Recently, this type of analysis has been extended to Drosophila, an ideal eukaryote for genetic studies. We will review here the genetic dissection of mitosis in Drosophila melanogaster, discussing recent findings of interest and the methodological problems that have been encountered.
Evidence mounts for the role of gap junctions during development
Authors: Green Colin R.
Published: February 2005

While evidence for the role of gap functions, particularly during development, has been mounting, it has remained largely correlative, linking structure with presumed functions. With the recent advent of functional antibodies raised to the junctional protein, however, it has become possible to study the role of gap junctions more directly. There is now considerable evidence indicating that they play a vital role in tissue pattern formation and differentiation by allowing direct cell‐to‐cell transfer of developmental signals or morphogens.
The role of interferon in the regulation of virus infections by cytotoxic lymphocytes
Authors: Welsh Raymond M. , Yang Hyekyung , Bukowski Jack F.
Published: February 2005

Interferon (IFN) induced during a virus infection mediates antiviral effects both by direct inhibition of virus replication and by influencing the proliferation, differentiation, and chemotaxis of cyto‐toxic lymphocytes which control the infection. Cells from tissue taken from virus‐infected mice are conditioned by IFN to resist lysis by natural killer (NK) cells, while they become increasingly susceptible to lysis by cytotoxic Tlymphocytes (CTL). This is due to marked IFN‐induced biochemical changes, including an up‐regulation of major histocompatibility antigens, which are targets for CTL. Cytopathic viruses, which inhibit cellular RNA and protein synthesis, render target cells refractory to IFN‐mediated protection against NK cells, thereby providing a mechanism for NK cells to mediate antiviral effect by preferentially lysing virus‐infected but not uninfected cells.
Cellular transformation, tyrosine kinase oncogenes, and the cellular adhesion plaque
Authors: Kellie Stuart
Published: February 2005

The study of adhesion plaques in normal and transformed cells provides a series of phenotypic markers by which the process of transformation can be followed. Several proteins which are concentrated in adhesion plaques have now been identified; a few of these can act as targets for tyrosine kinase. In an attempt to characterize the relationship between tyrosine phosphorylation and cell transformation, the reactions of three such proteins – vinculin, talin and integrin – with a range of tyrosine kinase oncogene products have been studied in detail.
On transition metal ions and protein interactions in chromatin
Authors: Saavedra Raul A.
Published: February 2005

Metal ions may play an essential role in chromatin organization and, thus, be main actors in the gene expression drama. A model is proposed here for the interaction of DNA‐binding transcriptional regulatory proteins with histone H3 via coordinated metal ions and discussed in relation to the conversion of nucleosomal ‘closed’ to ‘open’ states.
Protein structure determination by nuclear magnetic resonance
Authors: Cooke Robert M. , Campbell Iain D.
Published: February 2005

The solution structures of several small proteins have recently been determined from high‐resolution nuclear magnetic resonance data. The principal features of the methods available to do this are outlined here, together with the advantages, limitations and future prospects of the technique.
The mechanistic role of enhancer elements in eukaryotic transcription
Authors: Jeang Kuan‐Teh , Khoury George
Published: February 2005

Enhancer elements are short stretches of nucleotides operationally defined by their cis‐acting ability to increase the transcription of nearby genes. They function relatively independently of position, orientation, and distance. Some show narrow tissue specificity while others permit constitutive expression in many different cell types. Although the first enhancer was described for simian virus 40 (SV40) more than five years ago, its mechanism of action has remained unclear. This review describes some of the models proposed to explain the physical role of enhancers in eukaryotic transcription.
Neuropeptides, second messengers and insect molting
Authors: Gilbert Lawrence I. , Combest Wendell L. , Smith Wendy A. , Meller Victoria H. , Rountree Dorothy B.
Published: February 2005

Insect molting is elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands. Ecdysteroid synthesis in the prothoracic glands is controlled in large measure by a peptide hormone from the brain, prothoracicotropic hormone (PTTH), which exists in two forms and is released into the general circulation as a result of environmental and developmental cues. The means by which PTTH activates the prothoracic glands has been examined at the cellular level and the data reveal the involvement of cAMP, calcium, calmodulin, cAMP‐dependent protein kinase and the ultimate phosphorylation of a 34 kDa protein tentatively identified as ribosomal protein S6.
Pre‐implantation diagnosis
Authors: Monk Marilyn
Published: February 2005

The access to human pre‐implantation embryos that is afforded by procedures now developed for the treatment of infertility presents the possibility of very early prenatal diagnosis, before implantation in the uterus, of certain genetic diseases. Only the normal embryos would be replaced in the mother for initiation of implantation and pregnancy. Early experiments on a mouse model for Lesch‐Nyhan syndrome (HPRT‐deficiency) show that pre‐implantation diagnosis of genetic disease is feasible.
Bacterial RNA polymerase — the ultimate metabolic sensor?
Authors: Travers Andrew A.
Published: February 2005

The RNA polymerase of Enterobacteria senses the physiological state of the cell by interaction with signal molecules such as ppGpp and responds by altering the rate of initiation of rRNA and tRNA species so as to limit or enhance the capacity for further growth.
Anterior‐posterior pattern formation: An evolutionary perspective on genes specifying terminal domains
Authors: Strecker Teresa R. , Lengyel Judith A.
Published: February 2005

The Drosophila anterior‐posterior pattern genes of the terminal class, particularly the tailless gene, affect structures derived from the acron and the tail region of the embryo. These domains correspond in position and function to asegmental domains at the termini of annelids and more primitive insect embryos. This suggests that terminal genes in Drosophila may have originated in an ancestor common to both annelids and arthropods, and thus that the specification of termini in these metameric organisms is an ancient, evolutionarily conserved process.
Genetics of surface protein variation in Neisseria gonorrhoeae
Authors: Murphy George L. , Cannon Janne G.
Published: February 2005

Neisseria gonorrhoeae, the bacterium that causes the sexually transmitted disease gonorrhea, demonstrates extensive antigenic heterogeneity in its surface components. The organism has the capacity to switch on and off the synthesis of different versions of components such as pili, outer membrane proteins, and lipopolysaccharide. Recent studies have shown that the gonococcus uses novel and complex mechanisms, of types not described previously, to store different versions of genetic information for surface proteins, and to regulate expression of those genes.
Targeting of proteins into chloroplasts
Authors: Keegstra Kenneth , Bauerle Cynthia
Published: February 2005

Cytoplasmically synthesized proteins are directed into chloroplasts by amino terminal transit sequences of the precursor proteins. For proteins of the thylakoid lumen, transit sequences are also important in directing proteins to the lumen.
The control of pattern as seen in the integument of an insect
Authors: Wigglesworth V. B.
Published: February 2005

In recent years, the phenomena of hormonal control, embryonic determination and pattern formation have been receiving intensive scrutiny from molecular biologists. In the following «Roots» contribution, Professor Sir Vincent B. Wigglesworth reviews some of the seminal work that he did on these subjects in the insect Rhodnius prolixus.
The chromatin domain as a unit of gene regulation
Authors: Goldman Michael A.
Published: February 2005

The process by which the genetically identical cell lineages of a multicellular organism acquire the propensity to express distinct arrays of gene products is among the most significant and fascinating questions in modern biology. Not surprisingly, this complex process requires control at several levels, each level providing a condition that is necessary but not sufficient for transcription to occur. Evidence suggests that one level of control concerns a region of DNA much larger than the transcription unit itself – the chromatin domain. This domain must be in a specific chromatin conformation in order to permit transcription; other control mechanisms may be required to bring about overt transcription. A hypothesis concerning the nature of chromatin domains and the relationship between early replication and transcription potential is presented.
Principles of antibody catalysis
Authors: Lerner Richard A. , Benkovic Stephen J.
Published: February 2005

Antibodies have now been shown to catalyze a variety of chemical transformations, including hydrolytic, concerted, and bimolecular reactions. The inherent chirality of the antibody binding pocket has been exploited to exert precise stereochemical control over their catalyzed reactions. The mechanisms by which antibodies catalyze reactions are not expected to differ in any general way from those of natural enzymes. Antibodies use their binding energy to stabilize species of higher free energy which appear along the reaction coordinate or effect general acid/base catalysis. The advent of catalytic antibodies promises new catalysts that extend the range of catalysis by proteins to chemical transformations that were not required during the evolution of enzymes.
The Leghaemoglobins
Authors: Powell Richard , Gannon Frank
Published: February 2005

The importance of nitrogen fixation, in assimilation of atmospheric dinitrogen for eventual storage in plant proteins, has resulted in extensive study of both plant and bacterial genes involved in this process. To date, the major plant genes analysed are the leghaemoglobins. These are closely related to the animal globins, allowing us to compare their gene organization, expression and evolution. We review here the progress and results of leghaemoglobin analysis and the comparisons with the related animal globins.
The Gap junction proteins: Vive la différence!
Authors: Kistler Joerg , Bullivant Stanley
Published: February 2005

The intercellular junctions connecting the cytoplasms of fibre cells in the mammalian lens have until recently been regarded as a class of junction which is fundamentally different from that of the gap junctions in other organs. Recent observations, however, suggest that the lens junctions fit protein topology predictions common for all gap junctions. While the homologous peptide portions are predicted to form the channels, the divergent peptide portions of the gap junction polypeptides may adapt channel activity to the special tissue requirements.
The role of giant axons in studies of the nerve impulse
Authors: Keynes Richard D.
Published: February 2005

The large size of the individual axons in the motor nerves of certain invertebrates has facilitated technical approaches that were not feasible elsewhere. A brief account is given of the way in which giant axons have taken and held the lead in research on the mechanism of conduction.
Structural elements regulating zein gene expression
Authors: Thompson Gary A. , Larkins Brian A.
Published: February 2005

Zeins are a group of alcohol‐soluble proteins that are synthesized in the endosperm of developing maize seeds. These proteins are encoded by a large number of genes located on several chromosomes; based upon the number of mutants that have been isolated, zein gene regulation is complex. Comparisons of gene flanking regions reveal conserved sequences that may be important for their regulation. Studies of transformed plant tissues support the assertion that cis‐acting elements with the 5′ flanking regions of zein genes are required for accurate transcription. Although the genes are transcribed in transgenic tobacco and petunia plants, they are not properly regulated. This appears to be due to transcriptional effects rather than protein or mRNA instability.
Gene structure and function of granulocyte colony‐stimulating factor
Authors: Nagata Shigekazu
Published: February 2005

In the last few years, the molecular and genetic nature of the granulocyte colonystimulating factor, which controls proliferation and differentiation of neutrophils, has been characterized. Recent clinical application of G‐CSF proves that this hormone is effective in the treatment of patients suffering from neutropenia.
Evolutionary aspects of urea cycle enzyme genes
Authors: Takiguchi Masaki , Matsubasa Tadashi , Amaya Yoshihiro , Mori Masataka
Published: February 2005

The functions and expression pattern of urea cycle enzymes have undergone considerable changes during the course of evolution. Sequence analyses shows that urea cycle enzymes from mammals are homologous to microbial enzymes of the arginine‐metabolic pathway. Recently, an unexpected relationship was found between argininosuccinate lyase (EC 4.3.2.1), the fourth enzyme of the cycle, and δ‐crystallin, a lens structural protein of birds and reptiles.
The saga of IMAC and MIT
Authors: Sulkowski Eugene
Published: February 2005

Immobilized Metal‐ion Affinity Chromatography, IMAC, has been gaining in popularity as the purification technique of choice for proteins and peptides. IMAC of proteins on transition metals (Co, Ni, Cu, Zn) can be rationalized in terms of the coordination of histidine residues. Brief accounts of the principles of IMAC, its anticipated development and plausible applications are presented. Metal Ion Transfer, MIT, may offer an efficient means to deplete a metal ion from a metalloprotein or, conversely, to charge its apo form with a metal.
The carbonic anhydrases: Widening perspectives on their evolution, expression and function
Authors: Tashian Richard E.
Published: February 2005

Now, some 55 years after its discovery in bovine red cells, carbonic anhydrase (CA), in all its varied forms, continues to challenge and intrigue physiologists, biochemists and molecular geneticists. This is so because of an increasing awareness of the many apparently diverse functions of the different CA isozymes encoded by this large multigene family, the continuing discovery of new CA, or CA‐related, genes, and the extensive variation in their hormonal control, cellular expression and subcellular localization.
Do ribosomes regulate mitochondrial RNA synthesis?
Authors: Jacobs Howard T.
Published: February 2005

The levels of different classes of mitochondrially encoded transcripts are developmentally regulated in sea urchin embryos, as a result of selection between mutually exclusive synthetic pathways. I propose a simple model to explain these observations, based on a dual role for mitochondrial ribosomes and translation factors in RNA synthesis as well as in translation. This effect may be exerted either at the transcriptional or post‐transcriptional level (or both), and is potentially generalizable to mammalian mtDNA and to other systems.
Microtubules and specification of the dorsoventral axis in frog embryos
Authors: Elinson Richard P.
Published: February 2005

The body plan of the frog is set‐up by a rearrangement of the egg cytoplasm shortly after fertilization. Microtubules play several roles in this critical developmental event.
Morphogens in chick limb development
Authors: Brickell P. M. , Tickle C.
Published: February 2005

Retinoic acid is a good candidate for a morphogen in chick limb bud development. The challenge now is to determine how retinoic acid interacts with limb bud cells and how the retinoic acid signal is integrated with other signals to mould and pattern the developing limb.
Temporally regulated expression of insulin and insulin‐like growth factors and their receptors in early mammalian development
Authors: Heyner Susan , Smith Robert M. , Schultz Gilbert A.
Published: February 2005

Recent studies of early development in a number of ivertebrate and vertebrate species have suggested that growth factors and their receptors may play important roles in differentiation as well as cell proliferation. In the mouse embryo, the expression of the receptors for insulin and insulin‐like growth factors I and II (IGF‐I and ‐II) are temporally regulated. The ontogeny of receptor and ligand expression within the insulin and IGF gene family suggests that the very earliest stages of mammalian embryogenesis may be subject to regulation by autocrine and paracrine factors from maternal and embryonic sources.
Cell polarity and development of the first epithelium
Authors: Wiley Lynn M. , Kidder Gerald M. , Watson Andrew J.
Published: February 2005

In the 4 1/2 to 5 days between fertilization and implantation, the mouse conceptus must gain the abilities to implant and produce an embryo. Each of these is the sole developmental responsibility of one of two cell types forming the blastocyst, trophectoderm and inner cell mass (ICM), respectively. Trophectoderm is a polarized transporting epithelium while the ICM is an aggregate of non‐epithelial pluripotent stem cells. These two cell types originate from the division of polar blastomeres when their cleavage furrows parallel their apical surfaces. Blastomeres polarize in response to asymmetric cell–cell contact, and understanding the mechanism of this induction is regarded as the key to understanding the origin of trophectoderm and ICM. Here we propose a model based on transcellular ion current loops for the induction of cell polarity during the development of the first epithelium, trophectoderm.
Self‐incompatibility in flowering plants
Authors: Dickinson Hugh G.
Published: February 2005

Self‐pollination in some groups of plants is prevented by a sophisticated biochemical signalling system. The molecule active in the female emerges as a highly charged glycoprotein, but the identity of the male determinant remains unknown. Studies of both the molecular biology and the physiology of the interaction suggest that the female polypeptide belongs to a family of glycoproteins which may play an additional, and more general, role in pollination. Pollen compatibility is controlled by one of two genetic systems and new information indicates a mechanism by which they may have arisen, together with the different stigma types with which they are correlated.
Induction of a phosphomannosyl binding lectin activity in Giardia
Authors: Ward Honorine D. , Keusch Gerald T. , Pereira Miercio E. A.
Published: February 2005

Giardia lamblia, a protozoan parasite that causes widespread diarrheal disease, expresses a surface membrane associated lectin, taglin, which is specifically activated by limited proteolysis with trypsin, a protease that is present in abundance at the site of infection. When activated, taglin agglutinates enterocytes which are the cells to which the parasite adheres in vivo, and in addition, binds to isolated brush border membranes of these cells. These findings suggest that this lectin may be involved in the host‐parasite interaction. Taglin is most specific for terminal phosphomannosyl residues and its binding to red cells is mediated by cell surface phosphate residues. Hemagglutinating activity induced by taglin is most active at pH6.5 and is dependent on divalent cations. A monoclonal antibody to taglin reacts with the surface membrane of live trophozoites and recognizes a protein of 28/30 kDa in lysates of Giardia trophozoites, by immunoblotting. This finding is confirmed by direct demonstration of lectin activity by erythrocyte binding to proteins electroblotted to nitrocellulose, which revealed specific red cell binding to giardial protein bands in the same molecular weight range as those recognized by the monoclonal antibody.
Molecular machinery required for protein transport from the endoplasmic reticulum to the golgi complex
Authors: Hicke Linda , Schekman Randy
Published: February 2005

The cellular machinery responsible for conveying proteins between the endoplasmic reticulum and the Golgi is being investigated using genetics and biochemistry. A role for vesicles in mediating protein traffic between the ER and the Golgi has been established by characterizing yeast mutants defective in this process, and by using recently developed cell‐free assays that measure ER to Golgi transport. These tools have also allowed the identification of several proteins crucial to intracellular protein trafficking. The characterization and possible functions of several GTP‐binding proteins, peripheral membrane proteins, and an integral membrane protein during ER to Golgi transport are discussed here.