摘要:

AbstractIn the yeastsSaccharomyces cerevisiaeandSchizosaccharomyces pombe, the initiation of DNA replication is controlled at a point called START. At this point, the cellular environment is assessed; only if conditions are appropriate do cells traverse START, thus becoming committed to initiate DNA replication and complete the remainder of the cell cycle. Thecdc2+/CDC28+gene, encoding the protein kinase p34, is a key element in this complex control. The identification of structural and functional homologues of p34 suggests that it has a role in the control of DNA replication in all eukaryotes. TheWHI1+,CLN1+andCLN2+gene products, identified inS. cerevisiae, are positive regulators that function at START and may interact with p34. Determining how passing the START control point leads to the initiation of DNA replication is a major outstanding challenge in cell cycle studies.

ISSN:0265-9247    

DOI:10.1002/bies.950121002

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

年代:1990

数据来源: WILEY

摘要:

AbstractMesodermal cell differentiation begins in response to an inductive interaction early in frog development. In parallel with the recent finding that certain peptide growth factors can induce mesoderm, early cellular and genetic responses to the induction have been discovered. I review here recent work on these responses, work that aims to understand how cells respond to inducers to form the complex pattern of the vertebrate mesoderm.

ISSN:0265-9247    

DOI:10.1002/bies.950121003

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

年代:1990

数据来源: WILEY

摘要:

AbstractA vital process in maintaining a low genetic error rate is the removal of mismatched bases in DNA. The importance of this process inE. coliis demonstrated by the 100–1000 fold increase in mutation frequency observed in cells deficient in this repair system(1). Mismatches can arise as a consequence of recombination, errors in replication and as a result of spontaneous chemical deamination, the latter process resulting in an estimated twelve T:G mismatches per genome per day in mammalian cells(2). Recent studies, discussed here, provide evidence for the existence of specific mismatch repair systems in mammalian and human cell

ISSN:0265-9247    

DOI:10.1002/bies.950121004

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

年代:1990

数据来源: WILEY

摘要:

AbstractMuch progress has been made in recent years regarding the mechanisms of targeting of secretory proteins to, and across, the endoplasmic reticulum (ER) membrane. Many of the cellular components involved in mediating translocation across this bilayer have been identified and characterized. Polypeptide domains of secretory proteins, termed signal peptides, have been shown to be necessary, and in most cases sufficient, for entry of preproteins into the lumen of the ER. These NH2‐ terminal segments appear to serve multiple roles in targeting and translocation. The structural features which mediate their multiple functions are currently the subject of intense stud

ISSN:0265-9247    

DOI:10.1002/bies.950121005

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

年代:1990

数据来源: WILEY

摘要:

AbstractSeveral complementary approaches have been fruitful in the study of transport from the ER to the Golgi complex in yeast. Mutational analysis has led to the identification of genes required for this process, many of which are now being studied at the molecular and biochemical level. In the case ofSEC18, DNA sequence analysis has demonstrated homology to a factor needed for transport in mammalianin vitrosystems. In addition, the events that take place at this stage of the secretory pathway have been reconstitutedin vitro.

ISSN:0265-9247    

DOI:10.1002/bies.950121006

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121007

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121008

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

年代:1990

数据来源: WILEY

摘要:

AbstractSecretory proteins and membranes move in transfer vesicles from the rough endoplasmic reticulum through the transitional region to the outer saccule of the Golgi complex. In both arthropod and vertebrate cells, the GC beads are a characteristic structural component of the transitional region. The beads are particles about half the size of ribosomes arranged equidistantly from one another and the smooth face of the ER. In an active GC, the beads are in rings through which the ER membrane emerges to form transfer vesicles. The beads may be part of the energy‐dependent step required for the movement of proteins along the secretory pathway, since they lose their ring arrangement under conditions that lower cellular ATP. The beads are organizers for Golgi complexes in the sense that they are the first recognizable components of new GCs as they arise from ER. Arthropod GC beads, but not those of vertebrates, can be visualized through their reaction with bismuthin vivoand in fixed tissue. Useful paradigms for traffic between the ER and the GC need to combine structural and biochemical information. Insect fat body, with its readily resolvable bismuth‐stained beads and easily fractionated cell components may have particular value for this prob

ISSN:0265-9247    

DOI:10.1002/bies.950121009

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121010

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121011

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

年代:1990

数据来源: WILEY