EXO5-DNA structure and BLM interactions direct DNA resection critical for ATR-dependent replication restart

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α‐ketoglutarate delays age‐related fertility decline in mammals

The fecundity reduction with aging is referred as the reproductive aging which comes earlier than that of chronological aging. Since humans have postponed their childbearing age, to prolong the reproductive age becomes urgent agenda for reproductive biologists. In the current study, we examined the potential associations of α‐ketoglutarate (α‐KG) and reproductive aging in mammals including mice, swine, and humans. There is a clear tendency of reduced α‐KG level with aging in the follicle fluids of human. To explore the mechanisms, mice were selected as the convenient animal model. It is observed that a long term of α‐KG administration preserves the ovarian function, the quality and quantity of oocytes as well as the telomere maintaining system in mice. α‐KG suppresses ATP synthase and alterations of the energy metabolism trigger the nutritional sensors to down‐regulate mTOR pathway. These events not only benefit the general aging process but also maintain ovarian function and delay the reproductive decline. Considering the safety of the α‐KG as a naturally occurring molecule in energy metabolism, its utility in reproduction of large mammals including humans deserves further investigation.     

Mitotic drug targets

Mitosis is the key event of the cell cycle during which the sister chromatids are segregated onto two daughter cells. It is well established that abrogation of the normal mitotic progression is a highly efficient concept for anti‐cancer treatment. In fact, various drugs that target microtubules and thus interfere with the function of the mitotic spindle are in clinical use for the treatment of various human malignancies for many years. However, since microtubule inhibitors not only target proliferating cells severe side effects limit their use. Therefore, the identification of novel mitotic drug targets other than microtubules have gained recently much attention. This review will summarize the latest developments on the identification and clinical evaluation of novel mitotic drug targets and will introduce novel concepts for chemotherapy that are based on recent progress in our understanding how mitotic progression is regulated and how anti‐mitotic drugs induce tumor cell death. J. Cell. Biochem. 111: 258–265, 2010. © 2010 Wiley‐Liss, Inc.     

Cytogenetic studies of Haplopappus gracilis in both callus and suspension cell cultures

Summary Investigations have been carried out on karyotype change in both callus and suspension cell cultures of Haplopappus gracilis (2n=4). It has been found that polyploidization arises directly in culture to give up to six times the normal diploid chromosome number in some cultures. In polyploid cultures, both chromosome loss and chromosome rearrangements occur to give rise to aneuploid karyotypes displaying chromosomes which differ in morphology from the diploid set. Whole or partial chromosome loss has been observed in the form of lagging chromosomes and chromosome bridges at anaphase, and micronuclei, ring chromosomes and chromosome fragments at other stages in mitosis. C-banded preparations have confirmed the occurrence of chromosomal rearrangements. Comparative investigations suggest that (i) more polyploidy occurs in callus cultures than in suspension cell cultures, and (ii) the presence of cytokinin (kinetin) in the culture medium may reduce the extent of karyotype change.     

Genetic diversity among sublines originating from a single somatic hybrid cell of Duboisia hopwoodii + Nicotiana tabacum

Summary The genetic instability of an intertribal hybrid cell line, Duboisia hopwoodii + Nicotiana tabacum, obtained by mechanical isolation of a single hybrid cell was studied. Ten subclones of calli derived from this hybrid cell line were cultured for 3 years, and their genetic makeup clarified as to nuclear DNA content, chromosome constitution, and peroxidase isozymes. Nuclear DNA content differed in each subclone. In most subclones, mean DNA content was lower than the mean DNA content in the original hybrid cell line determined 1 year after fusion. This decrease in DNA content is partly attributable to the elimination of tobacco chromosomes that occurred in all subclones. The extent to which tobacco chromosomes were eliminated varied among the subclones — evidence that chromosome elimination occurred slowly. Peroxidase isozyme analysis indicated the loss of a tobacco-specific isozyme, thus confirming results obtained by chromosome analysis. Shoots regenerated from two hybrid subclones after 2 years were also heterogeneous in morphology and nuclear DNA content.     

Complete reversion of the abo phenotype in D. melanogaster occurs only when the blood transposon is lost from region 32E.

Summary The abnormal oocyte phenotype is characterized by instability, as shown by the loss and reappearance of the abo maternal effect under specific genetic conditions. Our previous finding that a correlation exists between the abo phenotype and the presence of a blood transposon in region 32E, led us to perform an extensive genetic and molecular analysis of the most significant aspects of the abo phenotype in different genetic backgrounds. The results of these experiments can be summarized as follows: Complete reversion occurs only when the blood transposon is lost, thus definitively demonstrating that the insertion of the blood transposon in region 32E is the molecular event that causes the pleiotropic abo phenotype. Partial reversion can also occur without loss of the transposon, indicating that different molecular pathways may be involved in the loss of the abo phenotype. Reappearance of the full abo phenotype can occur only in heterozygous lines constructed from partially revertant abo homozygous lines that have not lost the blood transposon.     

A 2.6 kb intron separates the signal peptide coding sequence of an anther-specific protein from the rest of the gene in sunflower

Summary Metabolism of sulfonylurea herbicides by Streptomyces griseolus ATCC 11796 is carried out via two cytochromes P-450, P-450_SU1 and P-450_SU2. Mutants of S. griseolus, selected by their reduced ability to metabolize a fluorescent sulfonylurea, do not synthesize cytochrome P-450_SU1 when grown in the presence of sulfonylureas. Genetic evidence indicated that this phenotype was the result of a deletion of > 15 kb of DNA, including the structural genes for cytochrome P-450_SU1 and an associated ferredoxin Fd-1 (suaC and suaB, respectively). In the absence of this monooxygenase system, the mutants described here respond to the presence of sulfonylureas or phenobarbital in the growth medium with the expression of only the suhC,B gene products (cytochrome P-450_SU2 and Fd-2), previously observed only as minor components in wild-type cells treated with sulfonylurea. These strains have enabled an analysis of sulfonylurea metabolism mediated by cytochrome P-450_SU2 in the absence of P-450_SU1, yielding an in vivo delineation of the roles of the two different cytochrome P-450 systems in herbicide metabolism by S. griseolus.