ISSN:0265-9247    

DOI:10.1002/bies.950160302

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

年代:1994

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950160303

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

年代:1994

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950160304

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

年代:1994

数据来源: WILEY

摘要:

AbstractIntercellular signaling plays an important role in spatially regulated developmental processes.Myxococcus xanthusC signal transmission during fruiting body formation requires motile, densely packed, well aligned cells. tThe fruiting body consists of two domains: an outer domain which has densely packed, well aligned, motile cells: and an inner domain of more loosely packed, non‐motile, sporulating cells. The two domains are characterized by different patterns of C‐dependent gene expression, which begins in the outer domain where C‐signaling is most efficient, and reaches its maximum in the inner domain. These domains may be maintained by a dynamic mechanism which relies on passive transport of the sporulating cells from the outer domain, where sporulation is initiated, to the inner domain by the motile cells in the outer d

ISSN:0265-9247    

DOI:10.1002/bies.950160305

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe DNA in a eukaryotic nucleus is packaged into a nucleosome array, punctuated by variations in the regular pattern. The local chromatin structure of inducible genes appears to fall into two categories: preset and remodeling. Preset genes are those in which the binding sites fortrans‐acting factors are accessible (;i.e. in a non‐nucleosomal, DNase I hypersensitive configuration) prior to activation. In response to the activation signal, positive factors bind tocis‐acting regulatory elements and trigger transcription with no major alterations in the chromatin structure of the promoter region. In contrast, remodeling genes are those in which some of the requiredcis‐acting regulatory elements are packaged into nucleosomes. The nucleosomes must be perturbed in response to an activation signal in order for thetrans‐acting factors to gain access tocis‐acting elements; a chromatin remodeling process which forms DNase I hypersensitive sites must occur. In both cases, precise positioning of nucleosomes along the promoter region of a gene appears to be critical for appropriate regulation of

ISSN:0265-9247    

DOI:10.1002/bies.950160306

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe cuticle of the nematodeCaenorhabditis elegansforms the barrier between the animal and its environment. In addition to being a protective layer, it is an exoskeleton which is important in maintaining and defining the normal shape of the nematode. The cuticle is an extracellular matrix consisting predominantly of small collagen‐like proteins that are extensively crosslinked. Although it also contains other protein and non‐protein compounds that undoubtedly play a significant part in its function, the specific role of collagen in cuticle structure and morphology is considered here. TheC. elegansgenome contains between 50 and 150 collagen genes, most of which are believed to encode cuticular collagens. Mutations that result in cuticular defects and grossly altered body form have been identified in more than 40 genes. Six of these genes are now known to encode cuticular collagens, a finding that confirms the importance of this group of structural proteins to the formation of the cuticle and the role of the cuticle as an exoskeleton in shaping the worm. It is likely that many more of the genes identified by mutations giving altered body form, will be collagen genes. Mutations in the cuticular collagen genes provide a powerful tool for investigating the mechanisms by which this group of proteins interact to form the nematode cuti

ISSN:0265-9247    

DOI:10.1002/bies.950160307

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

年代:1994

数据来源: WILEY

摘要:

AbstractA complex structure, visible by electron microscopy, surrounds each chromosome during mitosis. The organization of this structure is distinct from that of the chromosomes and the cytoplasm. It forms a perichromosomal layer that can be isolated together with the chromosomes. This layer covers the chromosomes except in centromeric regions. The perichromosomal layer includes nuclear and nucleolar proteins as well as ribonucleoproteins (RNPs). The list of proteins and RNAs identified includes nuclear matrix proteins (perichromin, peripherin), nucleolar proteins (perichro‐monucleolin, Ki‐67 antigen, B23 protein, fibrillarin, p103, p52), ribosomal proteins (S1) and snRNAs (U3 RNAs). Only limited information is available about how and when the perichromosomal layer is formed. During early prophase, the proteins extend from the nucleoli towards the periphery of the nucleus. Thin cordon‐like structures reach the nuclear envelope delimiting areas in which chromosomes condense. At telophase, the proteins are associated with the part of the chromosomes remaining condensed and accumulate in newly formed nucleoli in regions where chromatin is already decondensed. The perichromosomal layer contains several different classes of proteins and RNPs and it has been attributed various roles: (1) in chromosome organization, (2) as a barrier around the chromosomes, (3) involvement in compartmentation of the cells in prophase and telophase and (4) a binding site for chromosomal passenger proteins necessary to the early process of nuclear ass

ISSN:0265-9247    

DOI:10.1002/bies.950160308

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

年代:1994

数据来源: WILEY

摘要:

AbstractAdvances in the understanding of Ras oncoprotein function suggest novel points for anti‐tumor intervention. First, upstream‐acting guanine nucleotide exchange factors and SH2/SH3 domain‐containing adaptor proteins that link Ras with growth factor receptor tyrosine kinases have recently been characterized. Second, work on downstream‐acting Ras effector functions including the Ras GTPase‐activating protein (p120GAP) and the Raf kinase has revealed direct biochemical interactions that are functionally required for oncogenic Ras signalling. We summarize progress in these areas and discuss the potential for novel applications to anti‐cancer c

ISSN:0265-9247    

DOI:10.1002/bies.950160309

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

年代:1994

数据来源: WILEY

摘要:

AbstractSignal transduction via receptors for N‐formylmethionyl peptide chemoattractants (FPR) on human neutrophils is a highly regulated process which involves participation of cytoskeletal elements. Evidence exists suggesting that the cytoskeleton and/or the membrane skeleton controls the distribution of FPR in the plane of the plasma membrane, thus controlling the accessibility of FPR to different proteins in functionally distinct domains. In desensitized cells, FPR are restricted to domains which are depleted of G proteins but enriched in cytoskeletal proteins such as actin and fodrin. Thus, the G protein signal transduction partners of FPR become inaccessible to the agonist‐occupied receptor, preventing cell activation. The mechanism of interaction of FPR with the membrane skeleton is poorly understood but evidence is accumulating that suggests a direct binding of FPR (and other receptors) to cytoskeletal proteins such as ac

ISSN:0265-9247    

DOI:10.1002/bies.950160310

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe reovirus cell attachment protein σ1 is a lollipopshaped structure with the fibrous tail anchored to the virion. Since it interacts with the cell receptor, σ1 is a major determinant of reovirus infectivity and tissue tropism. Studies on its structure‐function relationships have been facilitated by the fact that protein σ1 produced in any expression system is capable of binding to cell receptors. The use of site‐specific and deletion mutants has led to the identification and characterization of its virion anchorage and receptor binding domains. Studies on the oligomeric status of σ1 have revealed that σ1 is a homotrimer and that two independent trimerization events at different loci (the N‐ and C‐terminal halves, respectively) of the protein, are involved in its generation. This also accounts for a clearly demonstrable dominant negative effect by a mutant subunit in a wild‐type/mutant σ1 heterotrimer. Current efforts are focused on the involvement of chaperones in the generation of σ1 and on events that take place upon σ1 binding to the cell receptor. Protein σ1 has therefore become an excellent model system for the study of both virus attachment and protein oligomerization and

ISSN:0265-9247    

DOI:10.1002/bies.950160311

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

年代:1994

数据来源: WILEY