Enhancement of Telomere-Plasmid Segregation by the X-Telomere Associated Sequence in Saccharomyces Cerevisiae Involves Sir2, Sir3, Sir4 and Abf1

We have previously shown that circular replicating plasmids that carry yeast telomere repeat sequence (TG(1-3)) tracts segregate efficiently relative to analogous plasmids lacking the TG(1-3) tract and this efficient segregation is dependent upon RAP1. While a long TG(1-3) tract is sufficient to improve plasmid segregation, the segregation efficiency of telomere plasmids (TEL-plasmids) is enhanced when the X-Telomere Associated Sequence (X-TAS) is also included on the plasmids. We now demonstrate that the enhancement of TEL-plasmid segregation by the X-TAS depends on SIR2, SIR3, SIR4 and ABF1 in trans and requires the Abflp-binding site within the X-TAS. Mutation of the Abflp-binding site within the X-TAS results in TEL-plasmids that are no longer affected by mutations in SIR2, SIR3 or SIR4, despite the fact that other Abflp-binding sites are present on the plasmid. Mutation of the ARS consensus sequence within the X-TAS converts the X-TAS from an enhancer element to a negative element that interferes with TEL-plasmid segregation in a SIR-dependent manner. Thus, telomere associated sequences interact with TG(1-3) tracts on the plasmid, suggesting that the TASs have an active role in modulating telomere function.     

Seasonal changes in the spermatogenic epithelium of adult Japanese macaques (Macaca fuscata fuscata)

A histological study was undertaken to clarify seasonal changes in the spermatogenic epithelium of Japanese macaques. Testicular tissue samples were excised by biopsies from five adult laboratory-maintained males in mating and non-mating seasons. The samples were fixed with Bouin's solution, embedded in paraffin, and stained with PAS and hematoxylin. Microscopic observations on cross-sections of seminiferous tubules revealed that the seminiferous epithelium in the mating season was thicker than in the non-mating season. PAS-stained granules were found in some of the dark A-type spermatogonia, which significantly increased in the non-mating season. Spermatids of the steps preceding the appearance of the acrosomic cap in stages I to III were observed significantly more often than those in the step coinciding with the formation of the acrosomic cap in stage IV. In stage I, the ratio of mature spermatids or spermatozoa to immature spermatids in the mating season was higher than that in the non-mating season. These findings suggest that spermiogenesis, as well as spermatocytogenesis, is inhibited in the non-mating season.     

Conversion of the Salmonella phase 1 flagellin gene fliC to the phase 2 gene fljB on the Escherichia coli K-12 chromosome.

The Escherichia coli-Salmonella typhimurium-Salmonella abortus-equi hybrid strain EJ1420 has the two Salmonella flagellin genes fliC (antigenic determinant i) and fljB (determinant e,n,x) at the same loci as in the Salmonella strains and constitutively expresses the fliC gene because of mutations in the genes mediating phase variation. Selection for motility in semisolid medium containing anti-i flagellum serum yielded 11 motile mutants, which had the active fliC(e,n,x) and silent fljB(e,n,x) genes. Genetic analysis and Southern hybridization indicated that they had mutations only in the fliC gene, not in the fljB gene or the control elements for phase variation. Nucleotide sequence analysis of the fliC(e,n,x) genes from four representative mutants showed that the minimum 38% (565 bp) and maximum 68% (1,013 bp) sequences of the fliC(i) gene are replaced with the corresponding sequences of the fljB(e,n,x) gene. One of the conversion endpoints between the two genes lies somewhere in the 204-bp homologous sequence in the 5' constant region, and the other lies in the short homologous sequence of 6, 8, or 38 bp in the 3' constant region. The conversions include the whole central variable region of the fljB gene, resulting in fliC(e,n,x) genes with the same number of nucleotides (1,503 bp) as the fljB gene. We discuss the mechanisms for gene conversion between the two genes and also some intriguing aspects of flagellar antigenic specificities in various Salmonella serovars from the viewpoint of gene conversion.     

scRNA-seq Analysis of Hemocytes of Penaeid Shrimp Under Virus Infection

Marine Biotechnology - The classification of cells in non-model organisms has lagged behind the classification of cells in model organisms that have established cluster of differentiation marker...     

Large Inversion in Escherichia Coli K-12 1485in between Inversely Oriented Is3 Elements near Lac and Cdd

A companion study has shown that the inversion carried by strain 1485IN has one terminus between lac and proC and the other between his and cdd of the normal strain. Starting with this mapping data, we have done molecular work demonstrating that the inversion occurred by recombination between inversely oriented two IS3 elements, one present near lac and the other near the cdd locus; i.e., the inversion is IN(is3B-is3E). Evidence supporting this conclusion includes: (i) Normal and inversion strains share two short regions with identical restriction maps. One of these regions is near lac and the other near cdd. (ii) IS3 homology was detected in each of the terminus regions of both the normal and inversion strains. (iii) The sequence on one side of the original IS3 element near lac has been exchanged with the sequence on one side of the IS3 near cdd. Whether the inversion has occurred by one event of homologous recombination between the two IS3 elements or has been caused by involvement of IS3 elements on an F factor is discussed. Another rearrangement, probably related to inversion and deletion, was detected between the IS3 and cdd of the inversion strain.     

Alteration of a DNA-dependent ATPase activity in xeroderma pigmentosum complementation group C cells.

DNA-dependent ATPase activities in crude extracts prepared from HeLa cells were separated into five peaks by fast protein liquid chromatography Mono Q column chromatography. Similar elution profiles were observed with the extracts from human cells normal in repair and xeroderma pigmentosum cells belonging to complementation groups A through G except for group C. An alteration in elution of one of the five ATPases, designated DNA-dependent ATPase Q1, was observed with a cell line of complementation group C. This alteration was observed with all tested cell lines that belonged to group C. ATPase Q1 in HeLa cell extracts exhibited about 2-fold higher activity with ultraviolet light-irradiated DNA as compared to that with non-irradiated DNA, whereas little difference in the effects of two DNAs was observed with the ATPase activities in the extract from group C cells.     

Termination complex in Escherichia coli inhibits SV40 DNA replication in vitro by impeding the action of T antigen helicase.

DNA replication terminus (ter)-binding protein (TBP) in Escherichia coli binds specifically to the terminus (ter) site, and the resulting complex severely blocks DNA replication in an unique orientation by inhibiting the action of helicases. To generalize the intrinsic nature of the orientated ter-TBP complex against various helicases, we tested the potential of the complex to inhibit the action of three helicases, DNA helicase I, simian virus 40 (SV40) large tumor (T) antigen, and helicase B, derived from F plasmid, SV40, and mouse FM3A cell, respectively. The complex impeded the unwinding activities of all tested helicases in a specific orientation, with the same polarity observed in case of blockage of a replication fork, and, as a result, there was a block of SV40 DNA replication in both crude and purified enzyme systems in vitro. As the specificity in polarity of inhibition extends to heterologous systems, there may be common structure/mechanism features in helicases.     

Kinetics of growth and lactic acid production in continuous and batch culture

Summary In a lactic acid fermentation by Streptococcus faecalis, the specific consumption rate of glucose (v) and the specific production rate of lactic acid () were represented by the following simple equations as functions of the specific growth rate (): 1/=(1/) + 1/ = (1/) + By use of data from a batch culture, these two equations were derived from enzyme kinetics of the product inhibition. These equations were successfully applied to the results of batch culture and chemostat culture. In addition, calculation of ATP yield by these equations agreed with the experimental results better than the conventional Leudeking-Piret type equation, which includes two terms associated with growth and not with growth. Correspondence to: H. Ohara     

Formation of diastereoisomeric 3a-hydroxypyrroloindoles from a tryptophan residue analog mediated by iron (II)-EDTA and L-ascorbate

Oxygenation of a tryptophan residue analog by ascorbate in the presence of catalytic amounts of iron(II) and ethylenediaminetetraacetic acid (EDTA) has been studied. Under physiological conditions, reaction of the tryptophan derivative (N-t-butoxycarbonyl-L-tryptophan) with Fe(II)-EDTA and ascorbate resulted mainly in the oxygenation of the indole moiety of the substrate. In this reaction, cis and trans diastereoisomeric alcohols 3a-hydroxy-1-t-butoxycarbonyl-1,2,3,3a,8,8a-hexahydropyrrolo[2,3- b]indoles have been successfully identified in the metal-catalyzed free radical oxidation of indole compounds. Hydroxylation at C-5 and C-6 and a ring opening reaction between C-2 and C-3 have also been confirmed. The reaction of Fe(II)-EDTA/ascorbate with the tryptophan derivative was apparently nonselective with regard to position and was significantly suppressed by the hydroxyl radical scavengers (mannitol and dimethylsulfoxide), suggesting the participation of the hydroxyl radical as the actual oxidizing species.