Distribution and Properties of Chromatin-Associated Nucleoside Triphosphate Diphosphatase Purified by a New Method

Chromatin-associated nucleoside triphosphate diphosphatase (NTDPase)activity was detected in Alaska pea plant only at the germinationstage in a study of the plant's development over 5 month fromthe dormant to fruiting stages. This enzyme activity was alsodetected in seedlings of several dicotyledonous plants includingsoybean, Usui pea, cowpea and cucumber, but almost none wasfound in monocotyledonous corn and rice plants. When the chromatin of pea epicotyl was fractionated into template-activeand -inactive forms by DNase II digestion, most of the NTDPaseactivity was found in the active chromatin. A new method to rapidly isolate and purify NTDPase from peaepicotyl chromatin was developed in which NTDPase was elutedwith a linear gradient of NaCl on a column packed with cellulosepowder and chromatin. DNA remained on the column and the elutedNTDPase was purified further by chromatography using trimethylamino-2-hydroxypropylcellulose (TMAP-cellulose) and a Sephadex G-100 column, whichgive chromatin 18-fold purer than the starting sample. This purified NTDPase was adsorbed by DNA-cellulose, which isfurther evidence that NTDPase is a kind of non-histone proteinassociated with DNA. Several cations including Ca^2$, Mg^2$, Mn^2$and Zn^2$ stimulated the enzyme activity, with the maximal eightfoldactivation by Ca^2$. NTDPase activity was clearly inhibited byKCN and pyrophosphate, but not by SH-blocking inhibitors andvarious metal chelators at 1 mM.     

Rambutan genome revealed gene networks for spine formation and aril development

Rambutan is a popular tropical fruit known for its exotic appearance, has long flexible spines on shells, extraordinary aril growth, desirable nutrition, and a favorable taste. The genome of an elite rambutan cultivar Baoyan 7 was assembled into 328 Mb in 16 pseudo-chromosomes. Comparative genomics analysis between rambutan and lychee revealed that rambutan chromosomes 8 and 12 are collinear with lychee chromosome 1, which resulted in a chromosome fission event in rambutan (n = 16) or a fusion event in lychee (n = 15) after their divergence from a common ancestor 15.7 million years ago. Root development genes played a crucial role in spine development, such as endoplasmic reticulum pathway genes, jasmonic acid response genes, vascular bundle development genes, and K⁺ transport genes. Aril development was regulated by D-class genes (STK and SHP1), plant hormone and phenylpropanoid biosynthesis genes, and sugar metabolism genes. The lower rate of male sterility of hermaphroditic flowers appears to be regulated by MYB24. Population genomic analyses revealed genes in selective sweeps during domestication that are related to fruit morphology and environment stress response. These findings enhance our understanding of spine and aril development and provide genomic resources for rambutan improvement.     

Prediction of Muscle Activities from Electrocorticograms in Primary Motor Cortex of Primates

Electrocorticography (ECoG) has drawn attention as an effective recording approach for brain-machine interfaces (BMI). Previous studies have succeeded in classifying movement intention and predicting hand trajectories from ECoG. Despite such successes, however, there still remains considerable work for the realization of ECoG-based BMIs as neuroprosthetics. We developed a method to predict multiple muscle activities from ECoG measurements. We also verified that ECoG signals are effective for predicting muscle activities in time varying series when performing sequential movements. ECoG signals were band-pass filtered into separate sensorimotor rhythm bands, z-score normalized, and smoothed with a Gaussian filter. We used sparse linear regression to find the best fit between frequency bands of ECoG and electromyographic activity. The best average correlation coefficient and the normalized root-mean-square error were 0.92±0.06 and 0.06±0.10, respectively, in the flexor digitorum profundus finger muscle. The δ (1.5∼4Hz) and γ2 (50∼90Hz) bands contributed significantly more strongly than other frequency bands (P<0.001). These results demonstrate the feasibility of predicting muscle activity from ECoG signals in an online fashion.     

Intermediate filaments with novel protein composition from certain goldfish cells

Using the conditions for vimentin filament recycling, intermediate filaments (approximately 10 nm) were prepared from the cytoskeleton of a goldfish tumor cell line (erythrophoroma or xanthophoroma). 2-D analysis showed unusual protein composition, with four proteins of molecular weights of 60, 45, 56 and 51 kilodaltons in ratios of approximately 4:4:1:1. These correspond to four of the major cytoskeletal proteins of both the tumor cells and normal xanthophores.     

Regulation of protein degradation in muscle by calcium. Evidence for enhanced nonlysosomal proteolysis associated with elevated cytosolic calcium

Calcium-dependent regulation of intracellular protein degradation was studied in isolated rat skeletal muscles incubated in vitro in the presence of a large variety of agents known to affect calcium movement and distribution. A23187, KC1, sucrose, and 8-(diethylamino)octyl-3,4, 5-trimethoxybenzoate hydrochloride increase proteolysis while tetracaine, verapamil, and low extracellular calcium caused significant decreases. Additionally, dantrolene decreases proteolysis in the presence of depolarizing levels of potassium, while it has no effect on degradation in normal media. The dose dependence of calcium ionophore A23187 on proteolysis and contracture tension are parallel. Furthermore, excess KC1 and hypertonic solutions increased protein degradation at doses reported to cause tension. Thus, the parallel increase in proteolysis and tension in response to various agents supports the hypothesis that protein degradation in muscle is regulated by calcium. To determine the responsible proteolytic systems involved in calcium-dependent degradation, the effect of different classes of protease inhibitors was tested. Addition of the inhibitors leupeptin and E-64-c blocked the A23187-induced increase in degradation. Since proteases sensitive to these agents are present in both the sarcoplasm and lysosomes, known lysosomotropic agents, methylamine and chloroquine, as well as 3-methyladenine, a specific autophagy inhibitor, were used in combination with A23187. These agents did not inhibit calcium ionophore-induced proteolysis, although these three agents selectively inhibited enhanced degradation seen in the absence of insulin, demonstrating an autophagic/lysosomal pathway in these muscles. Thus, our results suggest that nonlysosomal leupeptin- and E-64-c-sensitive proteases are responsible for calcium-dependent proteolysis in muscle.