No abstract

Post-translational modifications of histones, such as acetylation and phosphorylation, are highly conserved in eukaryotes and their combination enables precise regulation of many cellular functions. Recent studies using mass spectrometry have revealed various non-acetyl acylations in histones, including malonylation and succinylation, which change the positive charge of lysine into a negative one. However, the molecular function of histone malonylation or succinylation is poorly understood. Here, we discovered the functions of malonylation in histone H2A at lysine 119 (H2A-K119) in chromosome segregation during mitosis and meiosis. Analyses of H2A-K119 mutants in Saccharomyces cerevisiae and Schizosaccharomyces pombe showed that anionic mutations, specifically to aspartate (K119D) and glutamate (K119E), showed mis-segregation of the chromosomes and sensitivity to microtubule-destabilizing reagents in mitosis and meiosis. We found that the chromosomal localization of shugoshin proteins, which depends on Bub1-catalyzed phosphorylation of H2A at serine 121 (H2A-S121), was significantly reduced in the H2A-K119D and the H2A-K119E mutants. Biochemical analyses using K119-unmodified or -malonylated H2A-C-tail peptides showed that H2A-K119 malonylation inhibited the interaction between Bub1 and H2A, leading to a decrease in Bub1-dependent H2A-S121 phosphorylation. Our results indicate a novel crosstalk between lysine malonylation and serine/threonine phosphorylation, which may be important for fine-tuning chromatin functions such as chromosome segregation.

Lysine acylation of proteins is an essential chemical reaction for posttranslational modification and as a means of protein modification in various applications. N,N‐Dimethyl‐4‐aminopyridine (DMAP) derivatives are widely‐used catalysts for lysine acylation of proteins; however, the DMAP moiety mostly exists in a protonated, and thus deactivated, form under physiological conditions due to its basicity. An alternative catalytic motif furnishing higher acylation activity would further broaden the possible applications of chemical lysine acylation. We herein report that the hydroxamic acid‐piperidine conjugate Ph‐HXA is a more active catalytic motif for lysine acetylation than DMAP under physiological conditions. In contrast to DMAP, the hydroxamic acid moiety is mostly deprotonated under aqueous neutral pH, resulting in a higher concentration of the activated form. The Ph‐HXA catalyst is also more tolerant of deactivation by a high concentration of glutathione than DMAP. Therefore, Ph‐HXA might be a suitable catalytic motif for target protein‐selective and site‐selective acetylation in cells.

Asymmetric synthesis of methyl ester (4) of (؊)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oic acid (1), which exhibited the most potent activity for the prevention of incipient carcinogenesis among the isolated diterpenes from Thuja standishii and its related plants, was achieved by using methyl (؊)-1,4a-dimethyl-5-oxodecahydronaphthalene-1-carboxylate (5) as a strating material, which was easily prepared on gram scale by baker's yeast-catalyzed asymmetric reduction.

Inversion of diastereoselectivity caused by a change in substrate concentration was first observed in baker's yeast catalyzed reduction of s-symmetrical 2,2-dialkylated cyclopentan-1,3-diones 1,2 and cyclohexan-1,3-dione 20. The selectivity altered by degrees depending on the substrate concentration from 8 mM to 40 mM. Meanwhile, application of the yeast-catalyzed reduction to the hydrogenated compound (5) of 1 afforded a single diastereomer in good yield when the reaction was conducted in high substrate concentration (40 mM).Asymmetric reductions with biocatalysts have been widely utilized to provide chiral synthons in organic synthesis since the reaction can be conducted under mild conditions, for example, in aqueous media and at moderate temperature. 1 Baker's yeast is one of the best-used biocatalysts among them mainly because of high potency for the reduction of ketones and availability in large amount. 2 During our study on the application of the yeast-catalyzed reduction to s-symmetrical cyclic 1,3-diketones, which afforded optically active cyclic 3-hydroxyketones, we encountered an interesting phenomenon that the diastereomeric ratio of products was inverted by changing the concentration of a substrate in a couple of cases while keeping Prelog's rule where newly generated secondary alcohols had the S-configuration. 3 Here we would like to report the details of this phenomenon.Many studies on asymmetric reduction of 2,2-dialkylated cyclohexan-1,3-diones have been published and some of them reported practically excellent results, 4-6 and it is known that ratios of diastereomers obtained as products varied depending on chemical properties of alkyl groups on the C-2 quaternary carbon of the cyclohexan-1,3-diones. 7 However, almost nothing has been reported to date on the reduction of 2,2-dialkylated cyclopentan-1,3-diones with baker's yeast, except for the reduction of 2,2-dimethylcyclopentan-1,3-dione. 8 Moreover, s-symmetrical cyclohexan-1,3-diones carrying a long alkyl chain on the C-2 position have been scarcely adopted as substrates in the asymmetric reduction using baker's yeast. Therefore, we embarked on study of the application of baker's yeast catalyzed reduction to s-symmetrical derivatives of cyclopentan-1,3-dione and cyclohexan-1,3-dione, which carried a long alkyl chain and an ester on the terminal carbon.We started with the preparation of substrates 1-6 having methyl and another alkyl group on the C-2 position of cyclopentan-1,3-dione. The substrates 1 and 2 having an ethylene unit between the cyclic ketone and a,b-unsaturated ester were synthesized in good overall yield by Michael addition of carbanion generated from 2-methylcyclopenta-1,3-dione (7) to acrolein, followed by Wittig reaction. On the other hand, the substrates 3 and 4 having a methylene unit between the cyclic ketone and a,b-unsaturated ester were synthesized in three steps, i.e., allylation of 7, ozonolysis to afford aldehyde 8, and successive Wittig reaction. Then, hydrogenation of the double bond of 1 and 3 afforded 5 and 6, re...