CDC17: an essential gene that prevents telomere elongation in yeast

The CDC17 gene product performs an essential stage-specific function during the Saccharomyces cerevisiae cell cycle. When cdc17-1 strains are grown at the maximum permissive temperature, recombination is induced preferentially in the genetic interval of the chromosome closest to the telomere. Telomeres are longer in cdc17 strains than in CDC17 strains at the permissive temperature because of addition of sequence near or in the poly (C1-3A) telomeric DNA and become even longer when cells are propagated at elevated temperatures. The mitotic recombination events require RAD52 function, but telomere growth does not. Long telomeres are maintained for many generations when crossed into a CDC17+ background, suggesting that telomere length is largely conserved during replication. The altered telomere length phenotype of cdc17 mutations is recessive and coreverts and cosegregates with the temperature-sensitive lethal phenotype.     

Fluctuations of grass pollen content in the atmosphere of East Perugia and meteorological correlations (year 1989)

Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria.     

A resonance Raman study of Ambystoma tigrinum hemoglobins: evidence for intraspecies hemepocket variations

Using resonance Raman difference spectroscopy, the Raman-active vibrational modes of hemoglobins from adult, neotenic, and larval forms of the salamander, Ambystoma tigrinum have been compared to each other and to human hemoglobin. The local heme environment of the adult and neotenic proteins were identical and differed from that of the larval protein. Differences were observed in modes sensitive to porphyrin pi electron density and axial ligation. Systematic differences were also observed between human and adult salamander hemoglobins particularly in modes sensitive to the heme vinyl environment. The relationship between these environmental differences, oxygen binding affinity, and the effects of allosteric modulators are discussed.     

Developmental regulation of myelin basic protein expression in mouse brain

Developmental regulation of myelin basic protein expression in mouse brain has been examined by comparing the myelin basic protein coding potential of mRNA in vitro with the accumulation of myelin basic protein-related polypeptides in vivo. In vitro translation of mRNA isolated from mouse brain generated eight myelin basic protein-related polypeptides with apparent molecular weights of 34K, 30K, 29K, 26K, 21.5K, 18.5K, 17K, and 14K. A similar set of eight myelin basic protein-related polypeptides with corresponding molecular weights was identified in vivo when total brain proteins were analyzed by immunoblotting. Each of the myelin basic protein-related polypeptides shows a characteristic developmental profile in terms of mRNA level and rate of accumulation implying a complex developmental program of myelin basic protein gene expression with regulation and modulation at several different biosynthetic levels.     

Observing the Temperature Dependent Transition of the GP2 Peptide Using Terahertz Spectroscopy

The GP2 peptide is derived from the Human Epidermal growth factor Receptor 2 (HER2/nue), a marker protein for breast cancer present in saliva. In this paper we study the temperature dependent behavior of hydrated GP2 at terahertz frequencies and find that the peptide undergoes a dynamic transition between 200 and 220 K. By fitting suitable molecular models to the frequency response we determine the molecular processes involved above and below the transition temperature (T _D). In particular, we show that below T _D the dynamic transition is dominated by a simple harmonic vibration with a slow and temperature dependent relaxation time constant and that above T _D, the dynamic behavior is governed by two oscillators, one of which has a fast and temperature independent relaxation time constant and the other of which is a heavily damped oscillator with a slow and temperature dependent time constant. Furthermore a red shifting of the characteristic frequency of the damped oscillator was observed, confirming the presence of a non-harmonic vibration potential. Our measurements and modeling of GP2 highlight the unique capabilities of THz spectroscopy for protein characterization.     

Transposable element-induced mutations of the viviparous-1 gene in maize

The viviparous-1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator-induced mutant allele, vp1-mum-1, by transposable element tagging has allowed analysis of several transposon-induced vp1 mutants. In the vp1-Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C-terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator- derived allele, vp1-mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild-type vp1 expression to a mutant condition. The vp1-mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild-type germinal revertants derived from vp1-mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1-mum2 states that exhibit wild-type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1-mum2 somatic mutation.     

Tissue factor (coagulation factor III) inhibition by apolipoprotein A-II

Apolipoprotein A-II (apoA-II) has been shown to inhibit tissue factor participation in the activation of coagulation factor X by factor VIIa. The magnitude of inhibition was dependent on the concentration of the enzyme (factor VIIa) and substrate (factor X) present in the reaction. With factor VIIa at 0.86 nM, 0.41 microM apoA-II inhibited factor X activation as much as 50% at 200 nM factor X, with inhibition decreasing to 39% at 3 nM factor X. When factor X was held constant at 100 nM, 0.41 microM apoA-II inhibited its activation by 80% when factor VIIa was present at 26.7 pM, but the inhibition decreased to 47% when factor VIIa was increased to 1.75 nM. Kinetically, increasing apoA-II decreased the reaction Vmax. ApoA-II produced little effect on the apparent Km, but the apparent K1/2 for factor VIIa in the reaction increased as apoA-II concentration increased. In the presence of 0.75 pM bovine tissue factor, reconstituted with 4.31 microM phosphatidylserine-phosphatidylcholine (30:70, w/w) vesicles, and in the absence of apoA-II, the apparent Km was near 7 nM factor X when factor VIIa was present at 0.86 nM. Under the same conditions with factor X at 100 nM, the apparent K1/2 was near 56 pM factor VIIa. As apoA-II was added to 0.41 microM, the apparent K1/2 increased to about 200 pM factor VIIa. The aggregate results support a model in which apoA-II inhibits tissue factor potentiation of factor VIIa activity. Because the apparent K1/2 increases when apoA-II is added, the factor VIIa can apparently protect tissue factor from the effects of apoA-II. Thus, apoA-II appears to inhibit factor X activation by preventing the appropriate association of tissue factor with factor VIIa.     

Genetic analysis of human B cell hybridomas expressing a cross-reactive idiotype

We have examined the genetic basis for the expression of a human cross-reactive idiotype (CRI) commonly found on monoclonal IgM rheumatoid factors. The CRI was identified with a monoclonal antibody (17.109) and has been localized previously to the kappa-variable region. By using the human lymphoblastoid cell line WI-L2-729-HF2, and mononuclear cells from several sources, a panel of hybridomas was generated that produced 17.109 CRI-positive Ig. A recently cloned human germ-line V kappa III gene, Humkv305, served as a probe to identify genes which were rearranged and expressed in 17.109 CRI-positive and -negative hybridomas. This probe, when hybridized to human genomic DNA under stringent conditions, identified only two to five germ-line bands. In 10 separate 17.109 CRI-positive hybridoma clones, an additional rearranged V kappa band was identified. The probe did not anneal to rearranged V kappa bands in hybridoma clones that produced kappa-chains lacking the CRI. RNA dot-blot studies provided evidence for expression of genes hybridizing to the Humkv305 probe. The results indicate that the 17.109 CRI is a serologic marker for a single V kappa gene, or a small family of closely related V kappa genes, which is identified by the Humkv305 probe.     

Isolation and characterization of human VkIII germ-line genes. Implications for the molecular basis of human VkIII light chain diversity

To understand the relative importance of germ-line genes in the generation of the functional human antibody repertoire, it is first necessary to define the number of variable region genes and to determine their fine structure. We have focused on the human VkIII variable region gene family because of its association with autoantibodies. A human genomic library was screened with a VkIII cDNA probe and subsequently with a VkIII germ-line gene probe. Seven different VkIII clones were isolated and characterized by restriction mapping and sequence analyses. Three clones have identical restriction enzyme sites over a 12-kilobase (kb) region, contain identical sequences over an 895-base pair (bp) region, and thus are likely to be different isolates of the same human VkIII gene. Another two clones have identical restriction enzyme sites over a 5-kb region, are identical over a stretch of 905 bp sequenced, and likely represent independent isolates of another human VkIII gene. The remaining two VkIII clones consist of two additional VkIII genes which are homologous to each other, but are quite different from the first two VkIII genes. Thus, four new human VkIII genes were defined. Together with four other VkIII genes previously isolated by other investigators, a total of eight human VkIII germ-like genes have now been described. A comparison of the deduced amino acid sequences of these genes with the reported amino acid sequences of all human VkIII light chains suggests that at least one additional VkIII gene exists in the germ line. Among the eight identified human germ-line VkIII genes, three are pseudogenes. Of the remaining five potential functional genes, one gene seems to encode a majority of the VkIII light chains which have been sequenced. Possible explanations for this phenomenon are discussed.