scholarly journals Suppression of the bimC4 mitotic spindle defect by deletion of klpA, a gene encoding a KAR3-related kinesin-like protein in Aspergillus nidulans.

1993 ◽  
Vol 120 (1) ◽  
pp. 153-162 ◽  
Author(s):  
M J O'Connell ◽  
P B Meluh ◽  
M D Rose ◽  
N R Morris
Keyword(s):  
Aspergillus Nidulans ◽  
Mitotic Spindle ◽  
Structural Similarity ◽  
Temperature Sensitive ◽  
Gene Encoding ◽  
Expression Studies ◽  
Primary Amino ◽  
And Function ◽  
Spindle Function ◽  
The Relationship

To investigate the relationship between structure and function of kinesin-like proteins, we have identified by polymerase chain reaction (PCR) a new kinesin-like protein in the filamentous fungus Aspergillus nidulans, which we have designated KLPA. DNA sequence analysis showed that the predicted KLPA protein contains a COOH terminal kinesin-like motor domain. Despite the structural similarity of KLPA to the KAR3 and NCD kinesin-like proteins of Saccharomyces cerevisiae and Drosophila melanogaster, which also posses COOH-terminal kinesin-like motor domains, there are no significant sequence similarities between the nonmotor or tail portions of these proteins. Nevertheless, expression studies in S. cerevisiae showed that klpA can complement a null mutation in KAR3, indicating that primary amino acid sequence conservation between the tail domains of kinesin-like proteins is not necessarily required for conserved function. Chromosomal deletion of the klpA gene exerted no observable mutant phenotype, suggesting that in A. nidulans there are likely to be other proteins functionally redundant with KLPA. Interestingly, the temperature sensitive phenotype of a mutation in another gene, bimC, which encodes a kinesin-like protein involved in mitotic spindle function in A. nidulans, was suppressed by deletion of klpA. We hypothesize that the loss of KLPA function redresses unbalanced forces within the spindle caused by mutation in bimC, and that the KLPA and BIMC kinesin-like proteins may play opposing roles in spindle function.

Mutation in the bimD gene of Aspergillus nidulans confers a conditional mitotic block and sensitivity to DNA damaging agents.

Genetics ◽  
1993 ◽  
Vol 134 (4) ◽  
pp. 1085-1096
Author(s):  
S H Denison ◽  
E Käfer ◽  
G S May
Keyword(s):  
Aspergillus Nidulans ◽  
Leucine Zipper ◽  
Temperature Sensitive ◽  
Sequence Motifs ◽  
Mitotic Progression ◽  
Dna Damaging Agents ◽  
Mitotic Block ◽  
Increased Sensitivity ◽  
Carboxyl Terminal ◽  
The Relationship

Abstract Mutation in the bimD gene of Aspergillus nidulans results in a mitotic block in anaphase characterized by a defective mitosis. Mutation in bimD also confers, at temperatures permissive for the mitotic arrest phenotype, an increased sensitivity to DNA damaging agents, including methyl methanesulfonate and ultraviolet light. In order to better understand the relationship between DNA damage and mitotic progression, we cloned the bimD gene from Aspergillus. A cosmid containing the bimD gene was identified among pools of cosmids by cotransformation with the nutritional selective pyrG gene of a strain carrying the recessive, temperature-sensitive lethal bimD6 mutation. The bimD gene encodes a predicted polypeptide of 166,000 daltons in mass and contains amino acid sequence motifs similar to those found in some DNA-binding transcription factors. These sequences include a basic domain followed by a leucine zipper, which together are called a bZIP motif, and a carboxyl-terminal domain enriched in acidic amino acids. Overexpression of the wild-type bimD protein resulted in an arrest of the nuclear division cycle that was reversible and determined to be in either the G1 or S phase of the cell cycle. Our data suggest that bimD may play an essential regulatory role relating to DNA metabolism which is required for a successful mitosis.

scholarly journals Mechanical design principles of a mitotic spindle

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Jonathan J Ward ◽  
Hélio Roque ◽  
Claude Antony ◽  
François Nédélec
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Structural Integrity ◽  
Mechanical Design ◽  
Structural Components ◽  
Cell Type ◽  
And Function ◽  
Anaphase B ◽  
The Relationship ◽  
Spindle Structure

An organised spindle is crucial to the fidelity of chromosome segregation, but the relationship between spindle structure and function is not well understood in any cell type. The anaphase B spindle in fission yeast has a slender morphology and must elongate against compressive forces. This ‘pushing’ mode of chromosome transport renders the spindle susceptible to breakage, as observed in cells with a variety of defects. Here we perform electron tomographic analyses of the spindle, which suggest that it organises a limited supply of structural components to increase its compressive strength. Structural integrity is maintained throughout the spindle's fourfold elongation by organising microtubules into a rigid transverse array, preserving correct microtubule number and dynamically rescaling microtubule length.

scholarly journals Automated mitotic spindle tracking suggests a link between spindle dynamics, spindle orientation, and anaphase onset in epithelial cells

2017 ◽  
Vol 28 (6) ◽  
pp. 746-759 ◽  
Author(s):  
Matthew E. Larson ◽  
William M. Bement
Keyword(s):  
Mitotic Spindle ◽  
Spindle Positioning ◽  
Tissue Organization ◽  
Anaphase Onset ◽  
Spindle Dynamics ◽  
And Function ◽  
Spindle Position ◽  
The Relationship ◽  
Rotational Oscillations ◽  
Final Orientation

Proper spindle positioning at anaphase onset is essential for normal tissue organization and function. Here we develop automated spindle-tracking software and apply it to characterize mitotic spindle dynamics in the Xenopus laevis embryonic epithelium. We find that metaphase spindles first undergo a sustained rotation that brings them on-axis with their final orientation. This sustained rotation is followed by a set of striking stereotyped rotational oscillations that bring the spindle into near contact with the cortex and then move it rapidly away from the cortex. These oscillations begin to subside soon before anaphase onset. Metrics extracted from the automatically tracked spindles indicate that final spindle position is determined largely by cell morphology and that spindles consistently center themselves in the XY-plane before anaphase onset. Finally, analysis of the relationship between spindle oscillations and spindle position relative to the cortex reveals an association between cortical contact and anaphase onset. We conclude that metaphase spindles in epithelia engage in a stereotyped “dance,” that this dance culminates in proper spindle positioning and orientation, and that completion of the dance is linked to anaphase onset.

scholarly journals Isolation and Functional Analysis of a Gene, tcsB, Encoding a Transmembrane Hybrid-Type Histidine Kinase from Aspergillus nidulans

2002 ◽  
Vol 68 (11) ◽  
pp. 5304-5310 ◽  
Author(s):  
Kentaro Furukawa ◽  
Yasuaki Katsuno ◽  
Takeshi Urao ◽  
Tomio Yabe ◽  
Toshiko Yamada-Okabe ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Histidine Kinase ◽  
Phosphorylation Site ◽  
Structural Similarity ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Kinase Gene ◽  
Hybrid Type

ABSTRACT We cloned and characterized a novel Aspergillus nidulans histidine kinase gene, tcsB, encoding a membrane-type two-component signaling protein homologous to the yeast osmosensor synthetic lethal N-end rule protein 1 (SLN1), which transmits signals through the high-osmolarity glycerol response 1 (HOG1) mitogen-activated protein kinase (MAPK) cascade in yeast cells in response to environmental osmotic stimuli. From an A. nidulans cDNA library, we isolated a positive clone containing a 3,210-bp open reading frame that encoded a putative protein consisting of 1,070 amino acids. The predicted tcsB protein (TcsB) has two probable transmembrane regions in its N-terminal half and has a high degree of structural similarity to yeast Sln1p, a transmembrane hybrid-type histidine kinase. Overexpression of the tcsB cDNA suppressed the lethality of a temperature-sensitive osmosensing-defective sln1-ts yeast mutant. However, tcsB cDNAs in which the conserved phosphorylation site His552 residue or the phosphorelay site Asp989 residue had been replaced failed to complement the sln1-ts mutant. In addition, introduction of the tcsB cDNA into an sln1Δ sho1Δ yeast double mutant, which lacked two osmosensors, suppressed lethality in high-salinity media and activated the HOG1 MAPK. These results imply that TcsB functions as an osmosensor histidine kinase. We constructed an A. nidulans strain lacking the tcsB gene (tcsBΔ) and examined its phenotype. However, unexpectedly, the tcsBΔ strain did not exhibit a detectable phenotype for either hyphal development or morphology on standard or stress media. Our results suggest that A. nidulans has more complex and robust osmoregulatory systems than the yeast SLN1-HOG1 MAPK cascade.

Molecular characterization of protein O-mannosyltransferase and its involvement in cell-wall synthesis in Aspergillus nidulans

Microbiology ◽  
2004 ◽  
Vol 150 (6) ◽  
pp. 1973-1982 ◽  
Author(s):  
Takuji Oka ◽  
Tetsu Hamaguchi ◽  
Yuka Sameshima ◽  
Masatoshi Goto ◽  
Kensuke Furukawa
Keyword(s):  
Cell Wall ◽  
Aspergillus Nidulans ◽  
Protein Modification ◽  
Wild Type Strain ◽  
Wild Type ◽  
Gene Encoding ◽  
And Function ◽  
Encoding Protein

Protein O-glycosylation is essential for protein modification and plays important roles in eukaryotic cells. O-Mannosylation of proteins occurs in the filamentous fungus Aspergillus. The structure and function of the pmtA gene, encoding protein O-d-mannosyltransferase, which is responsible for the initial O-mannosylation reaction in Aspergillus nidulans, was characterized. Disruption of the pmtA gene resulted in the reduction of in vitro protein O-d-mannosyltransferase activity to 6 % of that of the wild-type strain and led to underglycosylation of an extracellular glucoamylase. The pmtA disruptant exhibited abnormal cell morphology and alteration in carbohydrate composition, particularly reduction in the skeletal polysaccharides in the cell wall. The results indicate that PmtA is required for the formation of a normal cell wall in A. nidulans.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

Structural similarity of ribosomes from E. coli and A. salina

1978 ◽  
Vol 36 (2) ◽  
pp. 242-243
Author(s):  
M. Boublik ◽  
R.M. Wydro ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Ribosomal Proteins ◽  
Direct Evidence ◽  
Structural Similarity ◽  
Carbon Support ◽  
Artemia Salina ◽  
Uranyl Acetate ◽  
Biological Assays ◽  
E Coli ◽  
And Function ◽  
Fine Carbon

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

Physicianship and the Rebirth of Medical Education

2018 ◽  
Author(s):  
J. Donald Boudreau ◽  
Eric Cassell ◽  
Abraham Fuks
Keyword(s):  
Medical Education ◽  
Educational Process ◽  
Medical Attention ◽  
Patient Centeredness ◽  
Goals Of Medicine ◽  
The Subject ◽  
Definition Of ◽  
And Function ◽  
William Osler ◽  
The Relationship

This book reimagines medical education and reconstructs its design. It originates from a reappraisal of the goals of medicine and the nature of the relationship between doctor and patient. The educational blueprint outlined is called the “Physicianship Curriculum” and rests on two linchpins. First is a new definition of sickness: Patients know themselves to be ill when they cannot pursue their purposes and goals in life because of impairments in functioning. This perspective represents a bulwark against medical attention shifting from patients to diseases. The curriculum teaches about patients as functional persons, from their anatomy to their social selves, starting in the first days of the educational program and continuing throughout. Their teaching also rests on the rock-solid grounding of medicine in the sciences and scientific understandings of disease and function. The illness definition and knowledge base together create a foundation for authentic patient-centeredness. Second, the training of physicians depends on and culminates in development of a unique professional identity. This is grounded in the historical evolution of the profession, reaching back to Hippocrates. It leads to reformulation of the educational process as clinical apprenticeships and moral mentorships. “Rebirth” in the title suggests that critical ingredients of medical education have previously been articulated. The book argues that the apprenticeship model, as experienced, enriched, taught, and exemplified by William Osler, constitutes a time-honored foundation. Osler’s “natural method of teaching the subject of medicine” is a precursor to the Physicianship Curriculum.

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