Acrosome reaction in sperm of the toad,bufo bufo japonicus

The acrosome in the sperm of the toad, Bufo bufo japonicus, consists of a membrane-limited acrosomal cap and a fibrous perforatorium. When sperm are incubated with the oviducal pars recta extract (PRE) for 30–60 min, the outer acrosomal membrane fuses with the overlying plasma membrane at several points with concomitant loss of the contents of the acrosomal cap. The inner acrosomal membrane thus exposed fuses with the plasma membrane at the caudal end of the acrosomal region. This PRE-induced acrosome reaction is completely inhibited by soybean trypsin inhibitor. Sperm found in the innermost jelly layer of inseminated eggs possess an intact acrosome, but those either passing through the vitelline coat or localizing in the perivitelline space are acrosome-reacted in the same manner as when treated with PRE. These observations, combined with recent evidence showing involvement of the pars recta substance in fertilization, indicate that the acrosome reaction occurring in a fertilizing sperm at or near the surface of the vitelline coat is a response to a substance that is derived from the pars recta and deposited in the vitelline coat.     

Detection of the Nicotiana rustica chloroplast genome coding for the large subunit of Fraction I protein in a somatic hybrid in which only the N. tabacum chloroplast genome appeared to have been expressed

Nine plants were produced from anthers of a somatic hybrid which had been obtained by fusion of Nicotiana tabacum L. and N. rustica L. protoplants. As determined by electrofocusing, the Fraction I protein of the original somatic hybrid had largesubunit polypeptides exclusively of the N. tabacum type. Two of the plants regenerated from anthers contained Fraction-I-protein large subunits exclusively of the N. rustica type. Since each plant was regenerated from a single cell, the somatic hybrid must have had cells containing both the N. tabacum and N. rustica chloroplast genome although the latter was not expressed. Possibilities to account for this non-expression of a chloroplast genome in the somatic hybrid are discussed.     

Predicted mode of intercalation of doxorubicin with dinucleotide dimers

Intermolecular molecular mechanics energy calculations have been carried out for doxorubicin interacting with two dinucleotide dimer sequences. The preferred mode of intercalation is in the minor groove with the anthraquinone ring of the drug nearly perpendicular to the base pairs for the (CpG) sequence having alternate C3′ endo-C2′ endo sugar ring puckering. The preferred intercalation conformation of the drug is nearly identical to the N-bromacetyldaunomycin crystal structure. This prediction is qualitatively consistent with the recently reported crystal structure of a d(CpGpCpGpCpG) dimer-daunomycin complex. For the other dinucleotide sequence, (TpC-ApG), minor groove intercalation is also preferred, but the drug conformation can be changed.     

Studies on the reaction intermediate of protocatechuate 3,4-dioxygenase. Formation of enzyme-product complex.

The nature of the oxygenated intermediate observed (Fujisawa, H., Hiromi, K., Uyeda, M., Okuno, S., Nozaki, M. and Hayaishi, O. (1972) J. Biol. Chem. 247, 4422--4428) during the reaction of protocatechuate 3,4-dioxygenase (protocatechuate:oxygen 3,4-oxidoreductase (decyclizing), EC 1.13.11.3) was investigated. 3,4-Dihydroxyphenylpropionic acid and 3,4-dihydroxyphenylacetic acid were used as substrates of the enzyme to slow down the rate of the reaction. The enzyme reactions were performed under conditions where the concentration of the organic substrate was lower than those of the enzyme and oxygen in the reaction mixture. The reactions were stopped before completion by the addition of hydrochloric acid or guanidine hydrochloride and then the organic compounds were extracted from the reaction mixture to be analyzed. The qualitative analyses by thin-layer chromatography revealed that there was no species other than the organic substrate and the enzymatic reaction end-product during reaction. The quantitative spectrophotometric analyses revealed that the organic substrate which had participated in the formation of the oxygenated intermediate existed as a species indistinguishable from the reaction end-product, indicating that the oxygenated intermediate was not a simple complex of oxygen, substrate and the enzyme, i.e., a ternary complex, but a species rather close to a binary complex of product and the enzyme.     

Proteasome-dependent degradation of replisome components regulates faithful DNA replication

The replication machinery, or the replisome, collides with a variety of obstacles during the normal process of DNA replication. In addition to damaged template DNA, numerous chromosome regions are considered to be difficult to replicate owing to the presence of DNA secondary structures and DNA-binding proteins. Under these conditions, the replication fork stalls, generating replication stress. Stalled forks are prone to collapse, posing serious threats to genomic integrity. It is generally thought that the replication checkpoint functions to stabilize the replisome and replication fork structure upon replication stress. This is important in order to allow DNA replication to resume once the problem is solved. However, our recent studies demonstrated that some replisome components undergo proteasome-dependent degradation during DNA replication in the fission yeast Schizosaccharomyces pombe. Our investigation has revealed the involvement of the SCF^Pof3 (Skp1-Cullin/Cdc53-F-box) ubiquitin ligase in replisome regulation. We also demonstrated that forced accumulation of the replisome components leads to abnormal DNA replication upon replication stress. Here we review these findings and present additional data indicating the importance of replisome degradation for DNA replication. Our studies suggest that cells activate an alternative pathway to degrade replisome components in order to preserve genomic integrity.     

miR-34a-5p might have an important role for inducing apoptosis by down-regulation of SNAI1 in apigenin-treated lung cancer cells

Molecular Biology Reports - Apigenin is a flavonoid with antioxidant and anticancer effects. It has been reported that apigenin inhibits proliferation, migration, and invasion and induces apoptosis...     

α-Synuclein and Neuronal Cell Death

Parkinson’s disease (PD) is a progressive neurodegenerative disorder affecting ～1 % of people over the age of 65. Neuropathological hallmarks of PD are prominent loss of dopaminergic (DA) neurons in the substantia nigra and formation of intraneuronal protein inclusions termed Lewy bodies, composed mainly of α-synuclein (αSyn). Missense mutations in αSyn gene giving rise to production of degradation-resistant mutant proteins or multiplication of wild-type αSyn gene allele can cause rare inherited forms of PD. Therefore, the existence of abnormally high amount of αSyn protein is considered responsible for the DA neuronal death in PD. Normally, αSyn protein localizes to presynaptic terminals of neuronal cells, regulating the neurotransmitter release through the modulation of assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex. On the other hand, of note, pathological examinations on the recipient patients of fetal nigral transplants provided a prion-like cell-to-cell transmission hypothesis for abnormal αSyn. The extracellular αSyn fibrils can internalize to the cells and enhance intracellular formation of protein inclusions, thereby reducing cell viability. These findings suggest that effective removal of abnormal species of αSyn in the extracellular space as well as intracellular compartments can be of therapeutic relevance. In this review, we will focus on αSyn-triggered neuronal cell death and provide possible disease-modifying therapies targeting abnormally accumulating αSyn.