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M Snyder

Publications and source records attributed to M Snyder.

At least 19 recordsLinked to original sources
PubMed1992

A homolog of the proteasome-related RING10 gene is essential for yeast cell growth.

Proteasomes are intracellular protein complexes displaying multiproteolytic activities. These complexes have been implicated in the antigen degradation process that generates peptides associated with the major histocompatibility complex (MHC) class-I molecule. RING10 and RING12 are genes encoded by the class-II region of the human MHC that have sequence homology to proteasome-encoding genes. We have identified a yeast gene, called PRG1, that encodes a protein predicted to contain 55.6% sequence identity to 80% of the RING10 gene product. Genomic disruption of PRG1 revealed that it is essential for yeast cell growth. These data strongly indicate that the antigen-processing system present in vertebrates evolved from a basic cellular process present in all organisms.

Amino Acid Sequence↗
PubMed1992

NuMA: an unusually long coiled-coil related protein in the mammalian nucleus.

A bank of 892 autoimmune sera was screened by indirect immunofluorescence on mammalian cells. Six sera were identified that recognize an antigen(s) with a cell cycle-dependent localization pattern. In interphase cells, the antibodies stained the nucleus and in mitotic cells the spindle apparatus was recognized. Immunological criteria indicate that the antigen recognized by at least one of these sera corresponds to a previously identified protein called the nuclear mitotic apparatus protein (NuMA). A cDNA which partially encodes NuMA was cloned from a lambda gt11 human placental cDNA expression library, and overlapping cDNA clones that encode the entire gene were isolated. DNA sequence analysis of the clones has identified a long open reading frame capable of encoding a protein of 238 kD. Analysis of the predicted protein sequence suggests that NuMA contains an unusually large central alpha-helical domain of 1,485 amino acids flanked by nonhelical terminal domains. The central domain is similar to coiled-coil regions in structural proteins such as myosin heavy chains, cytokeratins, and nuclear lamins which are capable of forming filaments. Double immunofluorescence experiments performed with anti-NuMA and antilamin antibodies indicate that NuMA dissociates from condensing chromosomes during early prophase, before the complete disintegration of the nuclear lamina. As mitosis progresses, NuMA reassociates with telophase chromosomes very early during nuclear reformation, before substantial accumulation of lamins on chromosomal surfaces is evident. These results indicate that the NuMA proteins may be a structural component of the nucleus and may be involved in the early steps of nuclear reformation during telophase.

Amino Acid Sequence↗
PubMed1992

The NUF1 gene encodes an essential coiled-coil related protein that is a potential component of the yeast nucleoskeleton.

In an attempt to identify structural components of the yeast nucleus, subcellular fractions of yeast nuclei were prepared and used as immunogens to generate complex polyclonal antibodies. One such serum was used to screen a yeast genomic lambda gt11 expression library. A clone encoding a gene called NUF1 (for nuclear filament-related) was identified and extensively characterized. Antibodies to NUF1 fusion proteins were generated, and affinity-purified antibodies were used for immunoblot analysis and indirect immunofluorescence localization. The NUF1 protein is 110 kD in molecular mass and localizes to the yeast nucleus in small granular patches. Intranuclear staining is present in cells at all stages of the cell cycle. The NUF1 protein of yeast is tightly associated with the nucleus; it was not removed by extraction of nuclei with nonionic detergent or salt, or treatment with RNAse and DNAse. Sequence analysis of the NUF1 gene predicts a protein 945 amino acids in length that contains three domains: a large 627 residue central domain predicted to form a coiled-coil structure flanked by nonhelical amino-terminal and carboxy-terminal regions. Disruption of the NUF1 gene indicates that it is necessary for yeast cell growth. These results indicate that NUF1 encodes an essential coiled-coil protein within the yeast nucleus; we speculate that NUF1 is a component of the yeast nucleoskeleton. In addition, immunofluorescence results indicate that mammalian cells contain a NUF1-related nuclear protein. These data in conjunction with those in the accompanying manuscript (Yang et al., 1992) lead to the hypothesis that an internal coiled-coil filamentous system may be a general structural component of the eukaryotic nucleus.

Amino Acid Sequence↗
PubMed1992

The nuclear-mitotic apparatus protein is important in the establishment and maintenance of the bipolar mitotic spindle apparatus.

The formation and maintenance of the bipolar mitotic spindle apparatus require a complex and balanced interplay of several mechanisms, including the stabilization and separation of polar microtubules and the action of various microtubule motors. Nonmicrotubule elements are also present throughout the spindle apparatus and have been proposed to provide a structural support for the spindle. The Nuclear-Mitotic Apparatus protein (NuMA) is an abundant 240 kD protein that is present in the nucleus of interphase cells and concentrates in the polar regions of the spindle apparatus during mitosis. Sequence analysis indicates that NuMA possesses an unusually long alpha-helical central region characteristic of many filament forming proteins. In this report we demonstrate that microinjection of anti-NuMA antibodies into interphase and prophase cells results in a failure to form a mitotic spindle apparatus. Furthermore, injection of metaphase cells results in the collapse of the spindle apparatus into a monopolar microtubule array. These results identify for the first time a nontubulin component important for both the establishment and stabilization of the mitotic spindle apparatus in multicellular organisms. We suggest that nonmicrotubule structural components may be important for these processes.

Anaphase↗
PubMed1992

Specification of sites for polarized growth in Saccharomyces cerevisiae and the influence of external factors on site selection.

Many eucaryotic cell types exhibit polarized cell growth and polarized cell division at nonrandom sites. The sites of polarized growth were investigated in G1 arrested haploid Saccharomyces cerevisiae cells. When yeast cells are arrested during G1 either by treatment with alpha-factor or by shifting temperature-sensitive cdc28-1 cells to the restrictive temperature, the cells form a projection. Staining with Calcofluor reveals that in both cases the projection usually forms at axial sites (i.e., next to the previous bud scar); these are the same sites where bud formation is expected to occur. These results indicate that sites of polarized growth are specified before the end of G1. Sites of polarized growth can be influenced by external conditions. Cells grown to stationary phase and diluted into fresh medium preferentially select sites for polarized growth opposite the previous bud scar (i.e., distal sites). Incubation of cells in a mating mixture results in projection formation at nonaxial sites: presumably cells form projections toward their mating partner. These observations have important implications in understanding three aspects of cell polarity in yeast: 1) how yeast cell shape is influenced by growth conditions 2) how sites of polarized growth are chosen, and 3) the pathway by which polarity is affected and redirected during the mating process.

Actins↗
PubMed1992

Short-term triazolam use improves nocturnal sleep of narcoleptics.

This study was undertaken to determine whether the use of triazolam by narcoleptic patients leads to improvement of nighttime sleep or excessive sleepiness. Ten narcoleptic patients, 5 males and 5 females, with complaints of sleep disturbance and aged between 18 and 60 years, were assigned to a single-blind within-subject crossover-designed study comparing placebo with 0.25 mg triazolam. All subjects completed sleep questionnaires and underwent 6 nights of polysomnographic testing. Following an adaptation night, subjects received either triazolam or placebo for 2 nights. Objective tests of sleepiness (multiple sleep latency testing/maintenance of wakefulness test) were performed. Sleep efficiency and overall sleep quality were improved on all triazolam nights. Daytime excessive sleepiness was not reduced objectively after triazolam. This study demonstrates that the short-term use of triazolam improves nocturnal sleep quality in narcoleptics. Studies of long-term administration of triazolam are required to determine if the improvement of nocturnal sleep is maintained.

Adult↗
PubMed1992

T-sleep: an improved method for scoring breathing-disordered sleep.

We developed a new method to score sleep fragmented by respiratory events that we call the T-sleep (transitional sleep scoring) method. Five control polysomnograms from subjects without sleep-related breathing abnormalities were scored by the Rechtschaffen and Kales (R&K) method, and 10 polysomnograms from patients with severe obstructive sleep apnea were scored by both the R&K and the T-sleep method. Comparative analyses were performed on sleep variables of the control and apnea polysomnograms, and interscorer correlations were assessed for sleep and apnea variables. The interscorer correlations were high for both R&K control scoring and for apnea recordings scored by the T-sleep method. The number of sleep stage events documented for the 10 apnea recordings was significantly less for the T-sleep method than the R&K method (36, SD 17.0 vs. 332, SD 144.0; p = 0.0002). The T-sleep method was shown to be an effective, accurate and quick method for scoring sleep in patients with sleep-related breathing disorders.

Adult↗
PubMed1992

The Rex system of bacteriophage lambda: tolerance and altruistic cell death.

The rexA and rexB genes of bacteriophage lambda encode a two-component system that aborts lytic growth of bacterial viruses. Rex exclusion is characterized by termination of macromolecular synthesis, loss of active transport, the hydrolysis of ATP, and cell death. By analogy to colicins E1 and K, these results can be explained by depolarization of the cytoplasmic membrane. We have fractionated cells to determine the intracellular location of the RexB protein and made RexB-alkaline phosphatase fusions to analyze its membrane topology. The RexB protein appears to be a polytopic transmembrane protein. We suggest that RexB proteins form ion channels that, in response to lytic growth of bacteriophages, depolarize the cytoplasmic membrane. The Rex system requires a mechanism to prevent lambda itself from being excluded during lytic growth. We have determined that overexpression of RexB in lambda lysogens prevents the exclusion of both T4 rII mutants and lambda ren mutants. We suspect that overexpression of RexB is the basis for preventing self-exclusion following the induction of a lambda lysogen and that RexB overexpression is accomplished through transcriptional regulation.

Adenosine Triphosphate↗
PubMed1992

CIK1: a developmentally regulated spindle pole body-associated protein important for microtubule functions in Saccharomyces cerevisiae.

A genetic screen was devised to identify genes important for spindle pole body (SPB) and/or microtubule functions. Four mutants defective in both nuclear fusion (karyogamy) and chromosome maintenance were isolated; these mutants termed cik (for chromosome instability and karyogamy) define three complementation groups. The CIK1 gene was cloned and characterized. Sequence analysis of the CIK1 gene predicts that the CIK1 protein is 594 amino acids in length and possesses a central 300-amino-acid coiled-coil domain. Two different CIK1-beta-galactosidase fusions localize to the SPB region in vegetative cells, and antibodies against the authentic protein detect CIK1 in the SPB region of alpha-factor-treated cells. Evaluation of cells deleted for CIK1 (cik1-delta) indicates that CIK1 is important for the formation or maintenance of a spindle apparatus. Longer and slightly more microtubule bundles are visible in cik1-delta strains than in wild type. Thus, CIK1 encodes a SPB-associated component that is important for proper organization of microtubule arrays and the establishment of a spindle during vegetative growth. Furthermore, the CIK1 gene is essential for karyogamy, and the level of the CIK1 protein at the SPB appears to be dramatically induced by alpha-factor treatment. These results indicate that molecular changes occur at the microtubule-organizing center (MTOC) as the yeast cell prepares for karyogamy and imply that specialization of the MTOC or its associated microtubules occurs in preparation for particular microtubule functions in the yeast life cycle.

Amino Acid Sequence↗
PubMed1992

A synthetic lethal screen identifies SLK1, a novel protein kinase homolog implicated in yeast cell morphogenesis and cell growth.

The Saccharomyces cerevisiae SPA2 protein localizes at sites involved in polarized cell growth in budding cells and mating cells. spa2 mutants have defects in projection formation during mating but are healthy during vegetative growth. A synthetic lethal screen was devised to identify mutants that require the SPA2 gene for vegetative growth. One mutant, called slk-1 (for synthetic lethal kinase), has been characterized extensively. The SLK1 gene has been cloned, and sequence analysis predicts that the SLK1 protein is 1,478 amino acid residues in length. Approximately 300 amino acids at the carboxy terminus exhibit sequence similarity with the catalytic domains of protein kinases. Disruption mutations have been constructed in the SLK1 gene. slk1 null mutants cannot grow at 37 degrees C, but many cells can grow at 30, 24, and 17 degrees C. Dead slk1 mutant cells usually have aberrant cell morphologies, and many cells are very small, approximately one-half the diameter of wild-type cells. Surviving slk1 cells also exhibit morphogenic defects; these cells are impaired in their ability to form projections upon exposure to mating pheromones. During vegetative growth, a higher fraction of slk1 cells are unbudded compared with wild-type cells, and under nutrient limiting conditions, slk1 cells exhibit defects in cell cycle arrest. The different slk1 mutant defects are partially rescued by an extra copy of the SSD1/SRK1 gene. SSD1/SRK1 has been independently isolated as a suppressor of mutations in genes involved in growth control, sit4, pde2, bcy1, and ins1 (A. Sutton, D. Immanuel, and K.T. Arnat, Mol. Cell. Biol. 11:2133-2148, 1991; R.B. Wilson, A.A. Brenner, T.B. White, M.J. Engler, J.P. Gaughran, and K. Tatchell, Mol. Cell. Biol. 11:3369-3373, 1991). These data suggest that SLK1 plays a role in both cell morphogenesis and the control of cell growth. We speculate that SLK1 may be a regulatory link for these two cellular processes.

Amino Acid Sequence↗
PubMed1991

Glucose induces cAMP-independent growth-related changes in stationary-phase cells of Saccharomyces cerevisiae.

Nutrients play a critical role in the decision to initiate a new cell cycle. Addition of nutrients to arrested cells such as stationary-phase cells and spores induces them to begin growth. We have analyzed the nutrients required to induce early cellular events in yeast. When stationary-phase cells or spores are incubated in the presence of only glucose, morphological and physiological changes characteristic of mitotically growing cells are induced and, in the absence of additional nutrients to support growth, the cells rapidly lose viability. Preincubation of stationary-phase cells in the presence of glucose decreases the time required to reach bud emergence upon the subsequent addition of rich medium. These processes are specifically induced by D-glucose and not by other components such as nitrogen source or L-glucose. The glucose-induced events are independent of the adenylate cyclase pathway, since strains with a temperature-sensitive mutation in either the adenylate cyclase gene (CDC35) or its regulator (CDC25) undergo glucose-induced cellular changes when incubated at the restrictive temperature. We suggest that glucose triggers events in the induction of a new mitotic cell cycle and that these events are either prior to the adenylate cyclase pathway or are in an alternative pathway.

Adenylyl Cyclases↗
PubMed1991

Segregation of the nucleolus during mitosis in budding and fission yeast.

The segregation of the nucleolus during mitosis was examined in Saccharomyces cerevisiae and Schizosaccharomyces pombe by indirect immunofluorescence using antibodies directed to highly conserved anti-nucleolus antigens. In mitotic S. pombe cells, the nucleolus appears to trail the bulk of the DNA. In wild-type cells of S. cerevisiae, the nucleolus segregates alongside the bulk of the genomic DNA. Based on its distance from the centromere, we would expect the rDNA in both organisms to segregate behind the majority of the genomic DNA, if telomeric regions trail centromeric regions as in other eukaryotes. We therefore suggest that in S. cerevisiae the nucleolus is attached to other parts of the nucleus which enable it to segregate along with the bulk of the DNA. The segregation of the nucleolus in topoisomerase mutants and nuclear division mutants of S. cerevisiae was also investigated. In cdc14 mutants which arrest at late anaphase, the vast majority of the DNA is separated, but the nucleolar antigens remain extended between the mother and daughter cells. Thus, the CDC14 gene of S. cerevisiae appears to be important for the separation of the nucleolus at mitosis.

Autoimmunity↗
PubMed1991

The KNS1 gene of Saccharomyces cerevisiae encodes a nonessential protein kinase homologue that is distantly related to members of the CDC28/cdc2 gene family.

A novel protein kinase homologue (KNS1) has been identified in Saccharomyces cerevisiae. KNS1 contains an open reading frame of 720 codons. The carboxy-terminal portion of the predicted protein sequence is similar to that of many other protein kinases, exhibiting 36% identity to the cdc2 gene product of Schizosaccharomyces pombe and 34% identity to the CDC28 gene product of S. cerevisiae. Deletion mutations were constructed in the KNS1 gene. kns1 mutants grow at the same rate as wild-type cells using several different carbon sources. They mate at normal efficiencies, and they sporulate successfully. No defects were found in entry into or exit from stationary phase. Thus, the KNS1 gene is not essential for cell growth and a variety of other cellular processes in yeast.

Amino Acid Sequence↗
PubMed1991

Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae.

The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC24 protein is directly or indirectly responsible for controlling the polarity of these proteins. Based on the cell cycle distribution of the SPA2 protein, a "cytokinesis tag" model is proposed to explain the mechanism of the non-random positioning of bud sites in haploid yeast cells.

Actins↗
PubMed1991

Neurological assessment: adaptations for special populations with mental retardation.

The incidence of mental retardation in the United States is approximately 125,000 births per year. Recent changes in government regulations necessitate that nurses caring for mentally retarded persons perform physical appraisals. These in-depth appraisals are a new skill for many nurses caring for the retarded and the routine neurological assessment processes must be modified in order to meet the special needs and behaviors of the mentally retarded population. This article provides examples of how a functional abilities approach to the neurological appraisal process can be modified. Further, two scenarios are presented to demonstrate how neurological data can be obtained from observing an individual's activities of daily living.

Activities of Daily Living↗
PubMed1991

Complex health problems. Clinically assessing self-management abilities.

Assessment of self-care abilities by staff nurses is critical to planning post-hospitalization care. Assessment instruments must be comprehensive and yet usable by busy nurses. Orem's three categories of self-care deficits (universal, developmental, and therapeutic) provided a basis for the development of a Self-Management Inventory.

Aged↗