摘要:

AbstractThe assembly of a bipolar spindle is essential for the accurate segregation of replicated chromosomes during cell division. Do chromosomes rely solely on other cellular components to regulate the assembly of the bipolar spindle or are they masters of their own fate? In the Zhang and Nicklas(1)study reviewed here, micromanipulation techniques and video microscopy were used to demonstrate the different roles that chromosome arms, kinetochores and centrosomes play in bipolar spindle assembly.

ISSN:0265-9247    

DOI:10.1002/bies.950171102

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe pathway for initiation of protein synthesis in eukaryotic cells has been defined and refined over the last 25 years using purified components andin vitroreconstituted systems. More recently, powerful genetic analysis in yeast has proved useful in unraveling aspects of translation inherently more difficult to address by strictly biochemical approaches. One area in particular is the functional analysis of multi‐subunit protein factors, termed eukaryotic initiation factors (eIFs), that play an essential role in translation initiation. eIF‐3, the most structurally complex of the eIFs, has until recently eluded this approach. The identification of the yeastGCD10gene as the structural gene for the ζ subunit of yeast eIF‐3(1)and the analysis of mutant phenotypes has opened the door to the genetic dissection of the eIF‐3 protein

ISSN:0265-9247    

DOI:10.1002/bies.950171103

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe mechanisms governing anterior‐posterior and dorsal‐ventral polarity inDrosophila melanogasterhad previously been considered as independent processes. However, two papers(1,2)now reveal that both axes are initiated during oogenesis by the same pathway, and also clearly demonstrate that one is dependent on the ot

ISSN:0265-9247    

DOI:10.1002/bies.950171104

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

年代:1995

数据来源: WILEY

摘要:

Abstractp53 is a multifunctional protein which plays a role in modulating gene transcription, policing cell cycle checkpoints, activating apoptosis, controlling DNA replication and repair, maintaining genomic stability and responding to genetic insults. Mutation of the p53 gene confers the single greatest known selective advantage favoring cancer formation. Point mutations result not only in the loss of tumor suppressor functions, but also in the gain of tumor promotion functions. These dual circumstances may be unique to p53 and, in part, could explain the relatively powerful force behind this selection pressure. General mechanisms of gain of function by mutated p53 may include alteration in transcriptional modulation and newly acquired targets for transcriptional regulation and protein binding. Despite the direct significance of p53 mutations, loss of the remaining wild‐type allele is usually required for the formation of tumors in the natural setting. Novel applications of the basic scientific knowledge of p53 could lead to an improvement in cancer treatment, hopefully in the not so distant futur

ISSN:0265-9247    

DOI:10.1002/bies.950171105

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

年代:1995

数据来源: WILEY

摘要:

AbstractDevelopment of an animal embryo involves the coordination of cell divisions, a variety of inductive interactions and extensive cellular rearrangements. One of the biggest challenges in developmental biology is to explain the relationships between these processes and the mechanisms that regulate them. Teleost embryos provide an ideal subject for the study of these issues. Their optical lucidity combined with modern techniques for the marking and observation of individual living cells allow high resolution investigations of specific morphogenetic movements and the construction of detailed fate maps. In this review we describe the patterns of cell divisions, cellular movements and other morphogenetic events during zebrafish early development and discuss how these events relate to the formation of restricted lineages.

ISSN:0265-9247    

DOI:10.1002/bies.950171106

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

年代:1995

数据来源: WILEY

摘要:

AbstractFragile X syndrome is the most common cause of inherited mental retardation in humans. The fragile X gene (FMR1) has been cloned and the mutation causing the disease is known. The molecular basis of the disease is an expansion of a trinucleotide repeat sequence (CGG) present in the first exon within the 5′ untranslated region of theFMR1gene. Affected individuals have repeat CGG sequences of above 200. As a result the gene is not producing protein. It has been shown that theFMR1protein has RNA binding activity, but the function of this RNA binding activity is not known. The timing and mechanism of repeat amplification are not yet understood. An animal model for fragile X syndrome has been generated, which can be used to study the clinical and biochemical abnormalities caused by absence ofFMR1protein produc

ISSN:0265-9247    

DOI:10.1002/bies.950171107

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

年代:1995

数据来源: WILEY

摘要:

AbstractAll organisms possess mechanisms to repair double strand breaks (dsbs) generated in their DNA by damaging agents. Site‐specific dsbs are also introduced during V(D)J recombination. Four complementation groups of radiosensitive rodent mutants are defective in the repair of dsbs, and are unable to carry out V(D)J recombination effectively. The immune defect in Severe Combined Immunodeficient (scid) mice also results from an inability to undergo effective V(D)J recombination, andscidcell lines display a repair defect and belong to one of these complementation groups. These findings indicate a mechanistic overlap between the processes of DNA repair and V(D)J recombination. Recently, two of the genes defined by these complementation groups have been identified and shown to encode components of DNA‐dependent protein kinase (DNA‐PK). We review here the three fields which have become linked by these findings, and discuss the involvement of DNA‐PK in dsb rejoining and in V(D)J recomb

ISSN:0265-9247    

DOI:10.1002/bies.950171108

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn the yeastSaccharomyces cerevisiaethree positive transcriptional control elements are activated by stress conditions: heat shock elements (HSEs), stress response elements (STREs) and AP‐1 responsive elements (AREs). HSEs bind heat shock transcription factor (HSF), which is activated by stress conditions causing accumulation of abnormal proteins. STREs mediate transcriptional activation by multiple stress conditions. They are controlled by high osmolarityviathe HOG signal pathway, which comprises a MAP kinase module and a two‐component system homologous to prokaryotic signal transducers. AREs bind the transcription factor Yap1p. The three types of control elements seem to have overlapping, but distinct functions. Some stress proteins encoded by HSE‐regulated genes are necessary for growth of yeast under moderate stress, products of STRE‐activated genes appear to be important for survival under severe stress and ARE‐controlled genes may mainly function during oxidative stress and in the response to toxic conditions, such as caused by heavy m

ISSN:0265-9247    

DOI:10.1002/bies.950171109

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

年代:1995

数据来源: WILEY

摘要:

AbstractActivation of resting T lymphocytes through the T cell antigen receptor complex is initiated by critical phosphorylation and dephosphorylation events that regulate the function and interaction of a number of signaling molecules. Key elements in these reactions are members of the Src, Syk and Csk families of protein tyrosine kinases (PTKs) and the phosphotyrosine phosphatases (PTPases) that regulate and/or counteract them, such as CD45. The PTKs can autophosphorylate and phosphorylate each other at multiple sites and, as the result of these interactions, they are induced to phosphorylate other cellular proteins. These phosphorylation events lead to modulation of enzymatic activities and/or serve as binding sites for other signaling molecules having phosphotyrosine‐binding Src homology 2 (SH2) domains. As a result, these proteins translocate to the receptor complexes and are juxtaposed to the kinases that phosphorylate them. Some of the SH2‐domain‐containing polypeptides lack enzymatic activities and, instead, serve as adapter molecules that couple the signal to downstream effectors, such as regulators of the Ras proteins, and further into serine/threonine‐specific protein kinase cascades. Through largely unknown steps these reactions lead to the transcription of previously silent genes, activation of lymphocyte effector functions, progression through the cell cycle and cell prolif

ISSN:0265-9247    

DOI:10.1002/bies.950171110

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe macrophage plays an important role in host development and physiology, and in pathogenesis of many infectious, immunologic and degenerative disease processes. It displays marked heterogeneity of phenotype in different tissues, reflecting local interactions with other cell types, and contributes to host homeostasis through a varied repertoire of plasma membrane and secretory molecules. Upon isolation from the body it continues to express special, as well as general, features of cellular organisation and function, which make it a delight to study in cell culture.

ISSN:0265-9247    

DOI:10.1002/bies.950171111

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

年代:1995

数据来源: WILEY