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11.
Enhanced Gene Conversion and Postmeiotic Segregation in Pachytene-Arrested SACCHAROMYCES CEREVISIAE 总被引:7,自引:4,他引:3
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Previous study has demonstrated that incubation of yeast cells of strain AP-1 in sporulation medium at 36° permits them to begin meiosis but that they become arrested at pachytene and undergo enhanced intragenic recombination between ade2 heteroalleles. Tetrad analysis was undertaken to characterize the altered program of meiotic recombination more widely. In one set of experiments, pachytene-arrested cells were permitted to resume sporulation upon transfer to the permissive temperature. In the resulting asci, both postmeiotic segregation and gene conversion were increased several-fold at a number of loci relative to unarrested controls, whereas reciprocal recombination increased two- to threefold. Another set of experiments analyzed the genetic consequences of inducing the pachytene-arrested cells to revert directly to mitotic growth without completion of meiosis. The appearance of homozygous sectors from heterozygous markers revealed that these cells had become committed to appreciable recombination but that reciprocal exchange was less frequent than in normal asci. Taken together, the data indicate that pachytene arrest rendered the cells committed to enhanced recombination upon resumption of sporulation but that most of the crossing over did not occur until release from the arrest. —The genetic basis of pachytene arrest by AP-1 was investigated by mating each of its parents with progeny of strain Y55, which is able to sporulate at 36°. Both of these diploids sporulated at 36°, and asci from the one studied further exhibited 2:2 segregation of the sporulation defect, indicating that pachytene arrest is dependent on a recessive, temperature-sensitive allele at a chromosomal locus. 相似文献
12.
The gene for human transforming growth factor alpha is on the short arm of chromosome 2 总被引:3,自引:0,他引:3
J V Tricoli H Nakai M G Byers L B Rall G I Bell T B Shows 《Cytogenetics and cell genetics》1986,42(1-2):94-98
Transforming growth factor alpha is a polypeptide growth factor that participates in the reversible transformation of cells in vitro and is secreted by many transformed cell lines. It also shares sequence and functional homologies with epidermal growth factor. Working with a cloned cDNA probe (lambda hTGF1-10) and derivatives, we have mapped this gene (TGFA) to 2p13 with the use of somatic cell hybrids and in situ hybridization. This is the same region involved in the 2;8 translocations of Burkitt lymphoma. Such a rearrangement could orient c-myc (8q24) adjacent to TGFA, resulting in activation of one or both of these genes. 相似文献
13.
The genes coding for insulin-like growth factors I and II and epidermal growth factor have been localized to human chromosomes 12q22----q24.1, 11p15, and 4q25----q27, respectively. 相似文献
14.
Osteogenesis imperfecta type IV: evidence of abnormal triple helical structure of type I collagen 总被引:4,自引:0,他引:4
Summary Skin fibroblasts from a patient with mild osteogenesis imperfecta (OI) type IV synthesize two populations of type I procollagen molecules. One population contains pro1(I) and pro2(I) chains that migrate normally in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and a second population contains only slower migrating pro1(I) and pro2(I) chains. The total amount of type I procollagen made by OI cells and the ratio of pro1(I): pro2(I) is normal. When labeled under conditions that inhibit post-translational modification of pro chains, the OI cells produce only single populations of pro1(I) and pro2(I) chains indicating that the apparent increased molecular weight of some OI pro chains is due to excessive post-translational modification rather than peptidyl insertions. Peptide maps indicate that excessive post-translational modification occurs along the entire triple helical segment of some 1(I) and 2(I) chains produced by OI cells. The effect of the mutation is to lower the melting temperature of the molecules containing slow migrating 1(I) and 2(I) chains to 39.5°C (compared to 41.5°C for control), and to delay secretion of the overmodified type I procollagen from OI cells. These data are consistent with a mutation near the carboxyl-terminal end of the triple helical domain which delays triple helical formation and renders all chains available for further post-translational modification amino-terminal to the mutation. Such alterations in triple helical structure, thermal stability, and secretion previously associated only with the lethal OI type II phenotype are thus also seen in the mild OI type IV phenotype. 相似文献
15.
MORPHOLOGICAL CHANGES AND THE REQUIREMENTS FOR MACROMOLECULE SYNTHESIS DURING EXCYSTMENT OF ACANTHAMOEBA CASTELLANII
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Light and phase-contrast microscopic observations of excystment in Acanthamoeba castellanii have been used to classify cells in excysting populations as free trophozoites, or mature, activated, or preemergent cysts. These categories have been used to describe the kinetics of excystment. A pH of 7 and a temperature of 30°C have been found to be optimal for the activation of mature cysts. Both activation and emergence are inhibited by cycloheximide and actinomycin D, but neither process is much affected by hydroxyurea. Cell-free extracts of high molecular weight components of cyst cytoplasm can support protein synthesis in vitro, although less efficiently than similar extracts from trophozoites. Evidence indicates that some of the functional RNA in the cyst extracts is synthesized before excystment. 相似文献
16.
Kinetics of radioactive iron transport were examined in three strains of Bacillus megaterium. In strain ATCC 19213, which secretes the ferric-chelating secondary hydroxamic acid schizokinen, 59Fe3+ uptake from 59FeCl3 or the ferric hydroxamate Desferal-59Fe3+ was rapid and reached saturation within 3 min. In strain SK11, which does not secrete schizokinen, transport from 59FeCl3 was markedly reduced; the two ferric hydroxamates Desferal-59Fe3+ or schizokinen-59Fe3+ increased both total 59Fe3+ uptake and the 59Fe3+ appearing in a cellular trichloroacetic acid-insoluble fraction, although 10 min was required to reach saturation. Certain characteristics of transport from both ferric hydroxamates and FeCl3 suggest that iron uptake was an active process. The growth-inhibitory effect of aluminum on strain SK11 was probably due to the formation of nonutilizable iron-aluminum complexes which blocked uptake from 59FeCl3. Desferal or schizokinen prevented this blockage. A strain (ARD-1) resistant to the ferric hydroxamate antibiotic A22765 was isolated from strain SK11. Strain ARD-1 failed to grow with Desferal-Fe3+ as an iron source, and it was unable to incorporate 59Fe3+ from this source. Growth and iron uptake in strain ARD-1 were similar to strain SK11 with schizokinen-Fe3+ or the iron salt as sources. It is suggested that the ferric hydroxamates, or the iron they chelate, may be transported by a special system which might be selective for certain ferric hydroxamates. Strain ARD-1 may be unable to recognize both the antibiotic A22765 and the structurally similar chelate Desferal-Fe3+, while retaining its capacity to utilize schizokinen-Fe3+. 相似文献
17.
18.
The induction of multinuclearity in agitated and in aging cultures of Acanthamoeba sp. Neff 总被引:1,自引:0,他引:1
Partially synchronized secondary cultures of chicken embryo fibroblasts were exposed to Rous sarcoma virus (RSV) at various times in the cell cycle. The initiation of normal virus production could be inhibited by treatment with excess thymidine or with cytosine arabinoside without any effect on mitosis. This result is consistent with the hypothesis that the provirus of RSV is DNA, although the virion of RSV contains only RNA. It was, also, found that treatment which prevented or interferred with the first mitosis after exposure to virus prevented the initiation of normal virus production. Later mitoses did not appear to be necessary. A corollary of this finding is that virus production is synchronized by mitosis and that the length of the latent period depends upon when in the cell cycle a cell is exposed to virus. 相似文献
19.
20.
Inoculum-dependent division lag of Bacillus cultures and its relation to an endogenous factor(s) ("schizokinen") 总被引:7,自引:3,他引:4
C E Lankford J R Walker J B Reeves N H Nabbut B R Byers R J Jones 《Journal of bacteriology》1966,91(3):1070-1079
Lankford, C. E. (The University of Texas, Austin), James R. Walker, James B. Reeves, N. H. Nabbut, B. R. Byers, and R. J. Jones. Inoculum-dependent division lag of Bacillus cultures and its relation to an endogenous factor(s) ("schizokinen"). J. Bacteriol. 91:1070-1079. 1966.-When cells of Bacillus megaterium, grown on Brain Heart Infusion Agar, were inoculated into a chemically defined medium, they exhibited a division lag which was an inverse function of inoculum size. The addition of filtrates of cultures from the same medium eliminated the inoculum-dependent component of lag, but not an inoculum-independent residual lag of constant duration. Culture filtrate of B. subtilis var. niger not only eliminated its inoculum-dependent lag but also was required to sustain exponential division. Dose-response and "growth time" bioassays, developed to measure lag-reducing activity of filtrates, demonstrated accumulation of active filtrate factor to a "critical" concentration prior to division initiation. Addition of this concentration to cultures eliminated the inoculum-dependent lag. Accumulation of the factor ceased temporarily at onset of division, but excretion was resumed later during exponential growth. Accumulation of a lag-reducing, cell-associated factor followed a similar course. Chromatographic and bioautographic analyses of culture filtrates of B. megaterium indicated that a single substance was primarily responsible for their activity. Results of dose-response tests for reciprocal activities of filtrates of different Bacillus species and strains suggested production of different factors by some, and of different quantities of similar factors by others. It is proposed that such endogenous factors which are synthesized and accumulate to a population-dependent concentration as a requisite to initiation and maintenance of division be designated as "schizokinens." 相似文献