RAG-heptamer interaction in the synaptic complex is a crucial biochemical checkpoint for the 12/23 recombination rule

In V(D)J recombination, the RAG1 and RAG2 protein complex cleaves the recombination signal sequences (RSSs), generating a hairpin structure at the coding end. The cleavage occurs only between two RSSs with different spacer lengths of 12 and 23 bp. Here we report that in the synaptic complex, recombination-activating gene (RAG) proteins interact with the 7-mer and unstack the adjacent base in the coding region. We generated a RAG1 mutant that exhibits reduced RAG-7-mer interaction, unstacking of the coding base, and hairpin formation. Mutation of the 23-RSS at the first position of the 7-mer, which has been reported to impair the cleavage of the partner 12-RSS, demonstrated phenotypes similar to those of the RAG1 mutant; the RAG interaction and base unstacking in the partner 12-RSS are reduced. We propose that the RAG-7-mer interaction is a critical step for coding DNA distortion and hairpin formation in the context of the 12/23 rule.     

Translation initiation AUG context varies with codon usage bias and gene length in Drosophila melanogaster

The relationship between the codon usage bias and the sequence context surrounding the AUG translation initiation codon was examined in 1100 Drosophila melanogaster mRNA sequences. The codon usage bias measured by the "codon adaptation index" (CAI), and the effectiveness of the AUG context for translation initiation assessed by the "AUG context adaptation index" (AUGCAI), showed a significant positive relationship (correlation coefficient: r = 0.34, p <0.0001), indicating that these two factors are evolutionally under a similar natural selection constraint at the translational level. The importance of each position of the AUG context in relation to codon usage bias was examined, and the preference for the nucleotide at the -13, -12, -11, -10, -7, -6, -5, -4, -3, -2, and -1 positions showed a significant positive correlation to the codon usage bias, suggesting the action of natural selection on these very specific positions of the Drosophila genome. The relationship between AUGCAI value and gene length was also examined, and a significant negative relationship was found (r = -0.15, p <0.0001), suggesting a general tendency of higher expressivity of shorter genes, and of lower expressivity of longer genes in D. melanogaster.     

Distribution of IL-5 receptor-positive B cells. Expression of IL-5 receptor on Ly-1(CD5)+ B cells.

mAb to murine IL-5R were prepared by means of fusion between mouse myeloma cells and spleen cells from a rat immunized with membrane-enriched fractions of IL-5-dependent early B cell line (T88-M). Two mAb (H7 and T21) were selected for their competitive inhibition of receptor binding by 35S-labeled IL-5 and of IL-5 biologic activities. The number of binding sites recognized by the mAb on different cell lines correlated with IL-5 responsiveness. Most surface IgM+ peritoneal B cells were H7+ and more than 70% were also Ly-1(CD5)dull+, and responded to IL-5 for polyclonal IgM production in a high frequency. A significant proportion of splenic B cells reacted with these mAb, although lower number (one-log less) than peritoneal B cells and a small proportion of H7dull+ splenic B cells seems to be Ly-1(CD5)dull+, 1 of 200 splenic B cells responded to IL-5 for IgM production. These results suggest that IL-5R+ B cells may consist of a subpopulation of B cells. Intriguingly, lymphoid populations of bone marrow cells were stained with H7 and T21, whereas myeloid populations were brightly stained with only T21. Finally, both H7 and T21 mAb specifically precipitated a protein of a Mr 60,000 from 125I-labeled cell lysates of IL-5R+ T88-M cells. The IL-5R with similar size (Mr 55,000 to 60,000) was precipitated from the cell lysates of peritoneal B cells. T21 mAb but not H7 mAb precipitated a protein of a Mr 110,000 from the cell lysates of bone marrow cells.     

Defects in reproductive functions in PACAP-deficient female mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a highly conserved neuropeptide and widely expressed in both brain and peripheral tissues, including several reproductive organs (e.g., testis and ovary). PACAP stimulates syntheses of several sexual hormones and steroids, suggesting it has possible roles in reproductive function. In this study, the role of PACAP in female reproductive functions such as fertility, mating behavior and maternal behaviors were investigated by using mice lacking PACAP (PACAP(-/-)). PACAP(-/-) females showed reduced fertility (the number of parturitions relative to the number of pairings). Mating experiments using vasectomized males revealed that mating frequency and its intervals in some PACAP(-/-) females were quite different (zero to eight times/4 weeks), whereas the frequency was relatively constant (two to three times/4 weeks) in wild-type females. In PACAP(-/-) females, maternal crouching behavior tended to decrease compared to wild-type females, although the influence of litter size on maternal behavior needs to be considered. These data suggest a role for endogenous PACAP in female reproductive processes.     

How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are differences between plant species in SL exudation under P- and N-deficient conditions, which may possibly be related to differences between legumes and non-legumes. To investigate this possibility in detail, the effects of N and P deficiencies on SL exudation were examined in Fabaceae (alfalfa and Chinese milk vetch), Asteraceae (marigold and lettuce), Solanaceae (tomato), and Poaceae (wheat) plants. In alfalfa as expected, and unexpectedly in tomato, only P deficiency promoted SL exudation. In contrast, in Chinese milk vetch, a leguminous plant, and in the other non-leguminous plants examined, N deficiency as well as P deficiency enhanced SL exudation. Distinct reductions in shoot P levels were observed in plants grown under N deficiency, except for tomato, in which shoot P level was increased by N starvation, suggesting that the P status of the shoot regulates SL exudation. There seems to be a correlation between shoot P levels and SL exudation across the species/families investigated.     

Preparation and biodegradability of chitin derivatives having mercapto groups

Cell walls of glasswort (Salicornia ramosissima Woods), a halophytic Chenopodiaceae, prepared as alcohol-insoluble solids, were found to be rich in arabinose, galacturonic acid, glucose and proteins, and contained 0·7% ferulic acid and 3·8% acetic acid. Pectic and hemicellulosic polysaccharides were extracted by cyclohexanediaminotetraacetic acid, hot dilute acid, cold dilute alkali and concentrated alkali (twice), with yields of 2·9, 19·1, 4·7, 7·4 and 1·9% of the alcohol-insoluble solids, respectively. Protein-rich material precipitated upon dialysis. The dialysed fractions were fractionated by ion-exchange chromatography, and the main fractions were analysed by gel-filtration and glycosyl linkage analysis. The hot acid extract contained 46·2% arabinose and 28·9% galacturonic acid, with high degrees of methylation and acetylation (65 and 45, respectively). It could be fractionated into a low-molecular-weight arabinan rich in ferulic acid, and a pectic fraction still relatively rich in neutral sugars. The concentrated alkali extracts were rich in xylose (33·4 and 23·6%, respectively). They were separated by ion-exchange chromatography into a fucogalactoxyloglucan and a glucuronoarabinoxylan.     

Biological Activity of the Constituents in Roots of Ezo-no-gishigishi (Rumex obtusifolius)

The roots of Ezo-no-gishigishi (Rumex obtusifolius) contained a high concentration of malonic acid (more than 100 mg/100 g fr.wt) and oxalic acid (15-45 mg/100g fr.wt). The effect of several compounds isolated from the roots of R. obtusifolius on the growth of some fungi, bacteria and lettuce seedlings was examined. It is suggested that one reason for the resistance to decomposition of roots of R. obtusifolius in soil is the existence of organic acids and derivatives of naphthalene and anthraquinone in the tissue.     

Expression of Arabidopsis MCA1 enhanced mechanosensitive channel activity in the Xenopus laevis oocyte plasma membrane

Higher plants sense and respond to osmotic and mechanical stresses such as turgor, touch, flexure and gravity. Mechanosensitive (MS) channels, directly activated by tension in the cell membrane and cytoskeleton, are supposed to be involved in the cell volume regulation under hypotonic conditions and the sensing of these mechanical stresses based on electrophysiological and pharmacological studies. However, limited progress has been achieved in the molecular identification of plant MS channels. Here, we show that MCA1 (mid1-complementing activity 1; a putative mechanosensitive Ca²⁺-permeable channel in Arabidopsis thaliana) increased MS channel activity in the plasma membrane of Xenopus laevis oocytes. The functional and kinetic properties of MCA1 were examined by using a Xenopus laevis oocytes expression system, which showed that MCA1-dependent MS cation currents were activated by hypo-osmotic shock or by membrane stretch produced by pipette suction. Single-channel analyses suggest that MCA1 encodes a possible MS channel with a conductance of 34 pS.