ISSN:0265-9247    

DOI:10.1002/bies.950160802

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

年代:1994

数据来源: WILEY

摘要:

AbstractHow motor proteins induce mechanical movement at the molecular level has been a focus of biophysicists for a long time. While the whole picture is yet to be completely revealed, recent developments in looking at nanometer‐scale movement with millisecond‐time resolution driven by single motors have revealed important new details about the moving step size and amount of force generated per molec

ISSN:0265-9247    

DOI:10.1002/bies.950160803

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe poly(A)‐dependent translational regulation of maternal mRNAs is an important mechanism to execute stage‐specific programs of protein synthesis during early development. This control underlies many crucial developmental events including the meiotic maturation of oocytes and activation of the mitotic cell cycle at fertilization. A recent report(1)demonstrates that the 3′ untranslated region of the cyclin A1, B1, B2 andc‐mosmRNAs determines the timing and extent of their cytoplasmic polyadenylation and translational activation duringXenopusoocyte maturation. These studies further establish that protein synthesis can be temporally and quantitatively controlled by developmentally regulated changes in the polyadenylation of materna

ISSN:0265-9247    

DOI:10.1002/bies.950160804

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

年代:1994

数据来源: WILEY

摘要:

AbstractDiseases caused bySalmonellaspecies are characterized by bacterial invasion of host cells.Salmonellainvasion requires a genetic locus (inv) with homology to bacterial systems involved in specific protein export and organelle assembly. Until recently, the actualSalmonellainvasion factors exported or assembled by theinvsystem remained unidentified. It now appears thatSalmonellaproduces novel appendages upon contact with host cells. These appendages are transient, appearing and disappearing rapidly from the bacterial surface. Appendages are altered in strains unable to invade due to mutations within theinv/spalocus. Therefore, a role for the invasion locus has been identified, providing another example of bacterial pathogens responding to signals provided by the host cell surface.

ISSN:0265-9247    

DOI:10.1002/bies.950160805

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

年代:1994

数据来源: WILEY

摘要:

AbstractA recent article by Rao(1)exemplifies a number of new trends in developmental biology, both of technical strategy and approach to the problem of neural induction. Rao introduced into frog embryos a mutant form of a mesodermal gene,Brachyury, and caused ectopic neural differentiation. This essay traces the route from the originalBrachyurymutation in mouse to the most likely conclusion of Rao's experiments — suggested previously(2)— that neural fate is a default path

ISSN:0265-9247    

DOI:10.1002/bies.950160806

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe organization of eukaryotic genomes as chromatin provides the framework within which regulated transcription occurs in the nucleus. The association of DNA with chromatin proteins required to package the genome into the nucleus is, in general, inhibitory to transcription, and therefore provides opportunities for regulated transcriptional activation. Granting access to thecis‐acting elements in DNA, a prerequisite for any further action of thetrans‐acting factors involved, requires the establishment of local heterogeneity of chromatin and, in some cases, extensive remodeling of nucleosomal structures. Challenging problems relate to the establishment of this heterogeneity at the level of the single nucleosome and to the mechanisms that operate when nucleosomal arrays are reorganized. Recent developments indicate that chromatin reconstitution in cell‐free systems allows the biochemical analysis of the interplay between transcription factors and chromatin components that brings about regulated transcri

ISSN:0265-9247    

DOI:10.1002/bies.950160807

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe use ofDrosophilachromosomal rearrangements and transposon constructs involving thewhitegene reveals the existence of repressive chromatin domains that can spread over considerable genomic distances. One such type of domain is found in heterochromatin and is responsible for classical position‐effect variegation. Another type of repressive domain is established, beginning at specific sequences, by complexes of Polycomb Group proteins. Such complexes, which normally regulate the expression of many genes, including the homeotic loci, are responsible for silencing,whitegene variegation, pairing‐dependent effects and insertional target

ISSN:0265-9247    

DOI:10.1002/bies.950160808

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

年代:1994

数据来源: WILEY

摘要:

AbstractMutations in specific genes result in birth defects, cancer, inherited diseases or lethality. The frequency with which DNA damage is converted to mutations increases dramatically when the cellular genome is replicated. Although DNA damage poses special problems to the fidelity of DNA replication, efficient mechanisms exist in mammalian cells which function to replicate their genome despite the presence of many damaged sites. These mechanisms operate in either error‐prone or error‐free modes of DNA synthesis, and frequently involve DNA strand‐pairing reactions. Genetic studies in yeast and other eukaryotes suggest that replication through DNA damage is highly regulated and catalysed by complex biochemical machineries composed of many specialised gene products. Knowledge of the molecular details by which such factors facilitate the replication of damaged DNA in mammalian cells should reveal basic rules about how DNA damage induces mutagenesis and carcinoge

ISSN:0265-9247    

DOI:10.1002/bies.950160809

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

年代:1994

数据来源: WILEY

摘要:

AbstractCurrently, a central question in biology is how signals from the cell surface modulate intracellular processes. In recent years phosphoinositides have been shown to play a key role in signal transduction. Two phosphoinositide pathways have been characterized, to date. In the canonical phosphoinositide turnover pathway, activation of phosphatidylinositol‐specific phospholipase C results in the hydrolysis of phosphatidylinositol 4,5‐bisphospate and the generation of two second messengers, inositol 1,4,5‐trisphosphate and diacylglycerol. The 3‐phosphoinositide pathway involves protein‐tyrosine kinase‐mediated recruitment and activation of phosphatidylinositol 3‐kinase, resulting in the production of phosphatidylinositol 3,4‐bisphosphate and phosphatidylinositol 3,4,5‐trisphosphate. The 3‐phosphoinositides are not substrates of any known phospholipase C, are not components of the canonical phosphoinositide turnover pathway, and may themselves act as intracellular mediators. The 3‐phosphoinositide pathway has been implicated in growth factor‐dependent mitogenesis, membrane ruffling and glucose uptake. Furthermore the homology of the yeast vps34 with the mammalian phosphatidylinositol 3‐kinase has suggested a role for this pathway in vesicular trafficking.In this review the different mechanisms employed by protein‐tyrosine kinases to activate phosphatidylinositol 3‐kinase, and its involvement in the signaling cascade initiated by tyrosine

ISSN:0265-9247    

DOI:10.1002/bies.950160810

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

年代:1994

数据来源: WILEY

摘要:

AbstractIntercellular signaling plays a major role in the development of vertebrate and invertebrate embryos. In several cases, including the induction of mesoderm and neural ectoderm induction inXenopusand the induction of the vulva inC. elegans, multiple intercellular signals are utilized. This review examines a number of examples of signaling in development wherein two signals combine to affect the fate of a cell. The examples are placed in distinct categories, based on whether the signals synergize with or antagonize one another, and on the inductive potential of the individual signals. These types of combinatorial signaling events are suggested to be a general feature of embryonic development.

ISSN:0265-9247    

DOI:10.1002/bies.950160811

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

年代:1994

数据来源: WILEY