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Biomedical subjects

M C Edwards

Publications and source records attributed to M C Edwards.

At least 19 recordsLinked to original sources
PubMed1998

Human cyclin K, a novel RNA polymerase II-associated cyclin possessing both carboxy-terminal domain kinase and Cdk-activating kinase activity.

The gene coding for human cyclin K was isolated as a CPR (cell-cycle progression restoration) gene by virtue of its ability to impart a Far- phenotype to the budding yeast Saccharomyces cerevisiae and to rescue the lethality of a deletion of the G1 cyclin genes CLN1, CLN2, and CLN3. The cyclin K gene encodes a 357-amino-acid protein most closely related to human cyclins C and H, which have been proposed to play a role in regulating basal transcription through their association with and activation of cyclin-dependent kinases (Cdks) that phosphorylate the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II (RNAP II). Murine and Drosophila melanogaster homologs of cyclin K have also been identified. Cyclin K mRNA is ubiquitously expressed in adult mouse and human tissues, but is most abundant in the developing germ cells of the adult testis and ovaries. Cyclin K is associated with potent CTD kinase and Cdk kinase (CAK) activity in vitro and coimmunoprecipitates with the large subunit of RNAP II. Thus, cyclin K represents a new member of the "transcription" cyclin family which may play a dual role in regulating Cdk and RNAP II activity.

Amino Acid Sequence↗
PubMed1997

Oat blue dwarf marafivirus resembles the tymoviruses in sequence, genome organization, and expression strategy.

The complete nucleotide sequence and genome organization of oat blue dwarf marafivirus (OBDV) were determined. The 6509 nucleotide RNA genome encodes a putative 227-kDa polyprotein (p227) with sequence motifs similar to the methyltransferase, papain-like protease, helicase, and polymerase motifs present in the nonstructural proteins of other positive strand RNA viruses. The 3' end of the open reading frame (ORF) that encodes p227 (ORF 227) also encodes the two capsid proteins: a 24-kDa capsid protein is presumably cleaved from the p227 polyprotein, whereas the 21-kDa capsid protein appears to be translated from a subgenomic RNA (sgRNA). Encoded amino acid and nucleotide sequence comparisons, as well as the OBDV genome expression strategy, show that OBDV closely resembles the tymoviruses. OBDV differs from the tymoviruses in its general biology, in its lack of a putative movement gene that overlaps the replication-associated genes, and in its fusion of the capsid gene sequences to the major ORF. OBDV also possesses a 3' poly(A) tail, as compared to the tRNA-like structures found in most tymoviral genomes. Due to the strong similarities in genome sequence and expression strategy, OBDV, and presumably the other marafiviruses, should be considered a member of the tymovirus lineage of the alpha-like plant viruses.

Amino Acid Sequence↗
PubMed1997

Human CPR (cell cycle progression restoration) genes impart a Far- phenotype on yeast cells.

Regulated cell cycle progression depends on the proper integration of growth control pathways with the basic cell cycle machinery. While many of the central molecules such as cyclins, CDKs, and CKIs are known, and many of the kinases and phosphatases that modify the CDKs have been identified, little is known about the additional layers of regulation that impinge upon these molecules. To identify new regulators of cell proliferation, we have selected for human and yeast cDNAs that when overexpressed were capable of specifically overcoming G1 arrest signals from the cell cycle branch of the mating pheromone pathway, while still maintaining the integrity of the transcriptional induction branch. We have identified 13 human CPR (cell cycle progression restoration) genes and 11 yeast OPY (overproduction-induced pheromone-resistant yeast) genes that specifically block the G1 arrest by mating pheromone. The CPR genes represent a variety of biochemical functions including a new cyclin, a tumor suppressor binding protein, chaperones, transcription factors, translation factors, RNA-binding proteins, as well as novel proteins. Several CPR genes require individual CLNs to promote pheromone resistance and those that require CLN3 increase the basal levels of Cln3 protein. Moreover, several of the yeast OPY genes have overlapping functions with the human CPR genes, indicating a possible conservation of roles.

Amino Acid Sequence↗
PubMed1996

Imprinting of the gene encoding a human cyclin-dependent kinase inhibitor, p57KIP2, on chromosome 11p15.

Parental origin-specific alterations of chromosome 11p15 in human cancer suggest the involvement of one or more maternally expressed imprinted genes involved in embryonal tumor suppression and the cancer-predisposing Beckwith-Wiedemann syndrome (BWS). The gene encoding cyclin-dependent kinase inhibitor p57KIP2, whose overexpression causes G1 phase arrest, was recently cloned and mapped to this band. We find that the p57KIP2 gene is imprinted, with preferential expression of the maternal allele. However, the imprint is not absolute, as the paternal allele is also expressed at low levels in most tissues, and at levels comparable to the maternal allele in fetal brain and some embryonal tumors. The biochemical function, chromosomal location, and imprinting of the p57KIP2 gene match the properties predicted for a tumor suppressor gene at 11p15.5. However, as the p57KIP2 gene is 500 kb centromeric to the gene encoding insulin-like growth factor 2, it is likely to be part of a large domain containing other imprinted genes. Thus, loss of heterozygosity or loss of imprinting might simultaneously affect several genes at this locus that together contribute to tumor and/or growth- suppressing functions that are disrupted in BWS and embryonal tumors.

Base Sequence↗
PubMed1996

A single nucleotide substitution in the alpha a gene confers oat pathogenicity to barley stripe mosaic virus strain ND18.

A 236-nucleotide region from the alpha a gene of strain CV42 (pathogenic to oat), when substituted for the homologous region in strain ND18 (nonpathogenic to oat), was shown previously to confer a near wild-type oat pathogenicity to this strain (Weiland and Edwards, 1994, Virology 201: 116-126). The data suggested that six amino acid substitutions in the alpha a gene were responsible for the differences in oat pathogenicity, and that threonine-724, encoded by CV42, might be a critical amino acid in determining pathogenicity of barley stripe mosaic virus (BSMV) to oat. In the present work, codons specifying T-724, I-764, and N-785 (encoded by CV42 RNA alpha) were substituted individually and in combination for those coding for P-724, T-764, and K-785 (encoded by ND18 RNA alpha), respectively, by site-directed mutagenesis. The core K-733, T-734, and K-736 positions (CV42) were substituted for Q-733, S-734, and Q-736 (ND18) as a single block. The results of inoculations with these mutants indicate that the C2261-->A2261 nucleotide substitution (P-724-->T-724) by itself is sufficient to enable strain ND18 to infect oat plants, although poorly. Additional substitution of CV42 codons into ND18 RNA alpha at the remaining five positions altered symptom type, decreased the timing of the appearance of symptoms, and increased the percentage of plants infected per inoculation. Nonetheless, all mutants accumulated to similar levels in inoculated oat protoplasts after a 24-h period. Using a recombinant RNA beta from which beta-glucuronidase could be expressed, results were obtained suggesting that the multiplication of strain ND18 and the nonpathogenic variants generated in the study was restricted in the inoculated leaf. The data indicate a potential pathway by which pathogenicity to oat evolved in BSMV.

Avena↗
PubMed1995

Multiple genetic loci within 11p15 defined by Beckwith-Wiedemann syndrome rearrangement breakpoints and subchromosomal transferable fragments.

Beckwith-Wiedemann syndrome (BWS) involves fetal overgrowth and predisposition to a wide variety of embryonal tumors of childhood. We have previously found that BWS is genetically linked to 11p15 and that this same band shows loss of heterozygosity in the types of tumors to which children with BWS are susceptible. However, 11p15 contains > 20 megabases, and therefore, the BWS and tumor suppressor genes could be distinct. To determine the precise physical relationship between these loci, we isolated yeast artificial chromosomes, and cosmid libraries from them, within the region of loss of heterozygosity in embryonal tumors. Five germ-line balanced chromosomal rearrangement breakpoint sites from BWS patients, as well as a balanced chromosomal translocation breakpoint from a rhabdoid tumor, were isolated within a 295- to 320-kb cluster defined by a complete cosmid contig crossing these breakpoints. This breakpoint cluster terminated approximately 100 kb centromeric to the imprinted gene IGF2 and 100 kb telomeric to p57KIP2, an inhibitor of cyclin-dependent kinases, and was located within subchromosomal transferable fragments that suppressed the growth of embryonal tumor cells in genetic complementation experiments. We have identified 11 transcribed sequences in this BWS/tumor suppressor coincident region, one of which corresponded to p57KIP2. However, three additional BWS breakpoints were > 4 megabases centromeric to the other five breakpoints and were excluded from the tumor suppressor region defined by subchromosomal transferable fragments. Thus, multiple genetic loci define BWS and tumor suppression on 11p15.

Base Sequence↗
PubMed1995

p57KIP2, a structurally distinct member of the p21CIP1 Cdk inhibitor family, is a candidate tumor suppressor gene.

Cyclin-dependent kinases (Cdks) are positive regulators of cell proliferation, whereas Cdk inhibitors (CKIs) inhibit proliferation. We describe a new CKI, p57KIP2, which is related to p21CIP1 and p27KIP1. p57KIP2 is a potent, tight-binding inhibitor of several G1 cyclin/Cdk complexes, and its binding is cyclin dependent. Unlike CIP1, KIP2 is not regulated by p53. Overexpression of p57KIP2 arrests cells in G1. p57KIP2 proteins have a complex structure. Mouse p57KIP2 consists of four structurally distinct domains: an amino-terminal Cdk inhibitory domain, a proline-rich domain, an acidic-repeat region, and a carboxy-terminal domain conserved with p27KIP1. Human p57KIP2 appears to have conserved the amino- and carboxy-terminal domains but has replaced the internal regions with sequences containing proline-alanine repeats. In situ hybridization during mouse embryogenesis revealed that KIP2 mRNA displays a striking pattern of expression during development, showing high level expression in skeletal muscle, brain, heart, lungs, and eye. Most of the KIP2-expressing cells are terminally differentiated, suggesting that p57KIP2 is involved in decisions to exit the cell cycle during development and differentiation. Human KIP2 is located at 11p15.5, a region implicated in both sporadic cancers and Beckwith-Wiedemann syndrome, a familial cancer syndrome, marking it as a candidate tumor suppressor. The discovery of a new member of the p21CIP1 inhibitor family with novel structural features and expression patterns suggests a complex role for these proteins in cell cycle control and development.

Amino Acid Sequence↗
PubMed1995

Finding prospective partners in the library: the two-hybrid system and phage display find a match.

The two-hybrid system uses the efficacy of yeast genetic assays to identify protein-protein interactions. It permits the rapid cloning of genes encoding products that interact with a given protein of interest. Also being developed are phage display methods that allow direct physical selection of binding proteins. These methods have significantly altered strategies for analysing signaling and regulatory pathways.

Bacteriophages↗
PubMed1995

Octreotide enhances positive calcium balance in Duchenne muscular dystrophy.

Although receptors for somatostatin are found in bone cells, the effect of somatostatin analogs on calcium metabolism is unknown. The authors studied, in a metabolic ward, the effect of octreotide (a long-acting somatostatin analog) and a placebo in two 6-day calcium balance periods in 8 children with Duchenne muscular dystrophy. As expected, octreotide (2 micrograms/kg, subcutaneously, every 8 hours) reduced serum growth hormone and somatomedin (IGF-1) to levels found in growth hormone deficiency. Octreotide enhanced calcium retention by 30% (96 mg daily [P < 0.04]) in 7 boys for whom complete data (diet, urine, and fecal calcium) were available. In 6 children with urinary calcium excretion (Uca) greater than 50 mg daily, octreotide markedly lowered Uca, from 114 +/- 23 mg daily to 61 +/- 9 mg daily (P < 0.03). Calcium retention occurred in patients with or without initial hypercalciuria, but the higher the basal Uca, the greater was the inhibition by octreotide (r = 0.79; P < 0.03). Inactive, nonambulatory patients had a more pronounced response of Uca to octreotide (P < 0.02). Octreotide caused a mild, nonsignificant reduction in fecal calcium, with no major changes in serum calcium, phosphorus, parathyroid hormone, urinary excretion of sodium and potassium, or in creatinine clearance. Based on the current observations and the presence of receptors for somatostatin in bone cells, this hormone may have, at least on a short-term basis, an anabolic effect on calcium, perhaps favoring its deposition in bone.

Adolescent↗
PubMed1994

Evidence that the alpha a gene of barley stripe mosaic virus encodes determinants of pathogenicity to oat (Avena sativa).

Complementary DNA clones from which infectious RNA can be transcribed were used to map the genetic determinants for oat (Avena sativa L.) pathogenicity of barley stripe mosaic virus (BSMV). Pseudorecombinant analysis of BSMV strains ND18 (nonpathogenic to oat) and CV42 (pathogenic to oat) indicated that the ability to systemically infect oat mapped to RNA alpha. A homologous recombinant of ND18 (18 alpha TKTKIN), possessing nucleotides 2218 to 2454 from CV42 RNA alpha, induced symptoms on oat similar to those generated by wild-type CV42. Six amino acids encoded by the alpha a gene differ between ND18 (PQSQTK) and CV42 (TKTKIN) in this region. Fine structure recombinants that encoded subsets of the six amino acid changes either were slow in their infection phenotype (18 alpha TKTK and 18 alpha TQSQIN) relative to recombinant 18 alpha TKTKIN or were not infectious (18 alpha KTKIN and 18 alpha KTK) to inoculated oat plants. Neither coat protein antigen nor viral RNA was detected in inoculated plants that did not display symptoms. All recombinants infected isolated oat protoplasts, however, as determined by Northern and Western blots of extracts from inoculated oat protoplasts. The accumulation of viral genomic RNAs in protoplasts among the recombinants tested was similar, except for that of recombinant 18 alpha TKTK which was reduced by 30%. The data support an earlier suggestion (Y. Zheng, and M. C. Edwards, 1990, J. Gen. Virol. 71, 1865-1868) that resistance of oat to BSMV strain ND18 is due to restricted virus movement in planta and provide evidence that the alpha a protein itself may be involved in the movement of BSMV in the infected plant.

Amino Acid Sequence↗
PubMed1994

Survey of pediatricians' management practices for recurrent abdominal pain.

Surveyed general pediatricians (N = 116) regarding six content areas: (a) diagnostic procedures utilized during the initial evaluation sequence of a child with recurrent abdominal pain (RAP); (b) factors that influence decisions to order additional evaluations; (c) management practices following negative evaluation results; (d) factors influencing decisions about consultation with or referral to a mental health professional; (e) attitudes about the etiology of RAP; and (f) the frequency in which pediatricians encountered children with RAP and referred them to mental health services. Results of this survey are presented and discussed from a biopsychosocial perspective. Limitations of the survey, implications of the results for integrating mental health professionals into the evaluation and treatment process of RAP patients, and directions for future research are discussed.

Abdominal Pain↗
PubMed1993

The effects of sodium loading on blood pressure and pain responses to the cold pressor test.

Two cold pressor tests were administered to 18 healthy normotensive males on two occasions, after 2 weeks of dietary sodium loading and after 2 weeks of maintaining their normal diet. While the addition of an extra 10 g/day of sodium to the diet had no overall effect on resting cardiovascular activity, it produced significantly greater diastolic blood pressure and smaller heart rate responses to the pain stimuli. As well, consistent with the large animal literature indicating a relationship between high blood pressure and diminished pain sensitivity, pain ratings were found to be significantly lower during the sodium loaded testing session. The ratings were corroborated by evidence of lower skin conductance reactivity to the second cold pressor test in the sodium loaded condition. Information concerning an elevation of risk for hypertension, perhaps provided by baroreceptors, may lead to compensatory reactions with hypoalgesia as one effect.

Adolescent↗
PubMed1993

Neurilemoma presenting as a painless mass on the dorsum of the foot.

The neurilemoma is a benign neoplasm of Schwann's cells arising from the sheath of a nerve. This neoplasm most commonly originates from the flexor surface of the body. An unusual presentation of a neurilemoma on the extensor surface of the foot was described. The treatment plan was explained, and pathologic characteristics were outlined. Trauma as a possible etiology was also described.

Foot Diseases↗
PubMed1992

RNA recombination in the genome of barley stripe mosaic virus.

Barley stripe mosaic Hordeivirus (BSMV) is a positive-strand RNA virus requiring three single-stranded RNAs (alpha, beta, and gamma) for infectivity. A terminal-sequence-dependent cloning strategy was used to clone the entire genome of the CV17 strain. Full-length gamma cDNA clones were obtained when oligonucleotides specific for the 5'-terminal sequence of RNA alpha were used in the cloning procedure, but not when RNA gamma-specific oligonucleotides were used. Sequence analysis of six putative gamma cDNA clones revealed that nucleotides 1-70 possess 89% homology with the first 70 nucleotides of RNA alpha. This leader region is separated from the gamma-specific coding region by an eight-base intervening sequence common to both CV17 RNAs alpha and gamma. Northern and Southern hybridization with oligonucleotide probes specific for either alpha or gamma leader sequences indicated that CV17 gamma cDNA clones are representative of native CV17 gamma RNAs. Furthermore, bioassays indicated that in vitro transcripts derived from these gamma cDNA clones were infectious when coinoculated with in vitro transcripts of full-length alpha and beta cDNA clones. Thus, the evidence suggests that RNA gamma of BSMV strain CV17 is a recombinant molecule which may have arisen as a result of natural recombination between RNAs alpha and gamma.

Base Sequence↗
PubMed1992

A human dimorphism resulting from loss of an Alu.

The molecular phylogeny of Alu and other repeated sequences in the human genome provides clues to events during primate evolution. A subclass of human Alu's has been previously identified as dimorphic insertions within members of the medium reiteration frequency (mer) class of repeats, reflecting the complicated sequence of insertion and radiation events leading to the current human genome structure. One dimorphic Alu is located within a previously unidentified mer family member, in the first intron of the human T4 (CD4) gene. The insertion (Alu+ allele) has a frequency of approximately 70% in Europeans and Africans and is homozygous in 20 Asian samples. Polymerase chain reaction amplification, direct DNA sequencing, and Southern analysis using oligonucleotide probes revealed that the Alu- allele was derived from the Alu+ allele by loss of part of the inserted sequence. Comparison with a tightly linked marker within the human genome and studies of baboon DNA samples revealed that the original insertion was a relatively early event in primate evolution, but that the Alu sequence loss leading to the dimorphism has occurred much more recently. Loss of Alu insertions therefore represents one mechanism for the generation of human Alu dimorphisms.

Animals↗