摘要:

AbstractMeasuring gene expression on a global scale has been one of the vexing problems of cell biology. Velculescuet al.(1)recently proposed a system for identifying gene expression levels based on very short sequence tags – about nine base pairs – located at a specific site within a gene transcript. By coupling the strategy to current automated sequencing machines and the large expressed sequence tag databases, it should be possible to follow changes in gene expression for large numbers of genes economically and accurat

ISSN:0265-9247    

DOI:10.1002/bies.950180402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractTheneuregulingene encodes a series of polypeptide growth factors that can influence the growth state of target vertebrate cells in culture. Recently, three studies have explored thein vivofunction of the neuregulin signaling system in mice by disrupting the genes encoding the neuregulin ligand(1)and two of its receptors, ErbB2(2)and ErbB4(3). Each of the genes is essential for development, and aberrations in cardiac and neural development are particularly prominent in mutant embryos. The observed defects, together with the localization of expression of the neuregulin signaling components within these tissues, highlight a paracrine mechanism for neuregulin‐mediated intercellular communicatio

ISSN:0265-9247    

DOI:10.1002/bies.950180403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA recent paper by Watabeet al.(1)describes the identification, in the promoter region of the organizer‐specific genegoosecoid, of two distinct growth factor responsive elements that are required for the regulation of this gene bothin vitroandin vivo. This is an important finding since it provides molecular evidence in support of the recently proposed model in which the production of dorsal type mesoderm is thought to require a synergistic interaction between a general mesoderm inducing factor and a dorsalizing competence modifier(2,6–8). Furthermore, the authors provide an elegant example of how a response element can become a useful tool to map the presence of a biologically available ligand within the emb

ISSN:0265-9247    

DOI:10.1002/bies.950180404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWithin the last five years, a number of specific growth factors have been localized in developing lesions of atherosclerosis. This localization of growth factors that is not observed in normal vessels, together with the pleotrophic activities of growth factors, have suggested a role for growth factors in atherosclerotic lesion progression. However, based onin vitrostudies, many of the growth factors identified in lesions have overlapping target cells and are derived from the same cellular sources. What is the relative role of the specific growth factors identified? How is the their activity altered by the local conditions in the vessel wall? How do different risk factors for atherosclerosis alter the balance between growth factors and their natural regulators? Evidence for the involvement of specific growth factors in the progression of lesions of atherosclerosis is discussed, as well as the multiple levels at which the activities of these growth factors may be regulated by the vessel wall.

ISSN:0265-9247    

DOI:10.1002/bies.950180405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAmong pathogenic micro‐organisms that evade the mammalian immune responses,Trypanosoma bruceihas developed the most elaborate capacity for antigenic variation. Trypanosomes branched early during eukaryotic evolution. They are characterized by many aberrations, ranging from the unusual compartmentation of metabolic pathways to the heresy of RNA editing. The ubiquitous phenomenon of glycosylphosphatidylinositol‐anchoring of eukaryotic plasma membrane proteins and RNAtrans‐splicing (trypanosome genes contain no introns), which adds an identical leader sequence to all trypanosome mRNAs, were first defined during studies of antigenic variation. Genetic transformation of trypanosomes and the high efficiency of gene targeting provide new opportunities to investigate the regulation of antigenic variation. There is every reason to expect trypanosomes to provide further surprises and insights into the evolution of genetic regulatory mecha

ISSN:0265-9247    

DOI:10.1002/bies.950180406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAssociation between sister chromatids is essential for their attachment and segregation to opposite poles of the spindle in mitosis and meiosis II. Sister‐chromatid cohesion is also likely to be involved in linking homologous chromosomes together in meiosis I. Cytological observations provide evidence that attachment between sister chromatids is different in meiosis and mitosis and suggest that cohesion between the chromatid arms may differ mechanistically from that at the centromere. The physical nature of cohesion is addressed, and proteins that are candidates for holding sister chromatids together are discussed. Dissolution of sister‐chromatid cohesion must be regulated precisely, and potential mechanisms to release cohesion are presen

ISSN:0265-9247    

DOI:10.1002/bies.950180407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractTelomeres are protective caps for chromosome ends that are essential for genome stability. Broken chromosomes missing a telomere will not be maintained unless the chromosome is ‘healed’ with the formation of a new telomere. Chromosome healing can be a programmed event following developmentally regulated chromosome fragmentation, or it may occur spontaneously when a chromosome is accidentally broken. In this article we discuss the consequences of telomere loss and the possible mechanisms that the enzyme telomerase employs to form telomeresde novoon broken chromosome e

ISSN:0265-9247    

DOI:10.1002/bies.950180408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractDivergent evolution can explain how many proteins containing structurally similar domains, which perform a variety of related functions, have evolved from a relatively small number of modules or protein domains. However, it cannot explain how protein domains with similar, but distinguishable, functions and similar, but distinguishable, structures have evolved. Examples of this are the RNA‐binding proteins containing the RNA‐binding domain (RBD), and a newly established protein group, the cold‐shock domain (CSD) protein family. Both protein domains contain conserved RNP motifs on similar single‐stranded nucleic acid‐binding surfaces. Apart from the RNP motifs, which have a similar function, the two families show little similarity in topology or amino acid sequence. This can be considered an interesting example of convergent evolution at the molecular level. Previously, a β‐sheet surface was found to interact with RNA in non‐homologous proteins from yeast, phage and man, revealing that this mode of RNA binding may be a widely r

ISSN:0265-9247    

DOI:10.1002/bies.950180409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe Y chromosomes of mostDrosophilaspecies are necessary for male fertility but they are not involved in sex determination. They have many puzzling properties that resemble the effects caused by B chromosomes. Classical genetic and molecular studies reveal substantial affinities between Y and B chromosomes and suggest that the Y chromosomes ofDrosophilaare not degenerated homologues of the X chromosomes, but rather that their Y chromosomes evolved as specialized supernumeraries similar to classical B chromosomes.

ISSN:0265-9247    

DOI:10.1002/bies.950180410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractTranscription and DNA supercoiling are known to be linked by a cause‐effect relationship that operates in both directions. It is proposed here that this two‐way relationship may be exploited by theE. coligenome to facilitate constitutive transcription of supercoil‐sensitive genes by polymerase batteries made up of uniformly spaced RNA polymerase elongation complexes. Specifically, it is argued that (1) polymerases transcribing DNA in tandem cooperate to relax each other's transcription‐driven positive supercoils; and (2) negative supercoils driven upstream by elongation complexes tend to be ‘harnessed’ and used to cooperatively (and periodically) initiate fresh transcription from promoters. Harnessing of transcription‐driven negative supercoils is thought to be achieved through the erection of protein barriers to the rotational upstream propagation of supercoils from transcription events. The possible relevance of such cooperation amongst polymerases to the activation of transcription by DNA‐binding protein factors is emphasized. Some testable predictions are made and implication

ISSN:0265-9247    

DOI:10.1002/bies.950180411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY