Dietary Resistant Starch Reduces Levels of Glucose-Dependent Insulinotropic Polypeptide mRNA along the Jejunum-Ileum in Both Normal and Type 2 Diabetic Rats

It has been reported that the circulating glucose-dependent insulinotropic polypeptide (GIP) levels were reduced by an intake of some foods/drugs capable of delaying carbohydrate digestion/absorption. In this study, we revealed that feeding rats with dietary resistant starch reduced the GIP mRNA levels along the entire length of the jejunoileum in both Wistar and type 2 diabetic GK rats.     

Inactivation of the Glucose-Dependent Insulinotropic Polypeptide Receptor Improves Outcomes following Experimental Myocardial Infarction

1. Download high-res image (275KB)
2. Download full-size image

     

Dissecting the Molecular Roles of Histone Chaperones in Histone Acetylation by Type B Histone Acetyltransferases (HAT-B)

The HAT-B enzyme complex is responsible for acetylating newly synthesized histone H4 on lysines K5 and K12. HAT-B is a multisubunit complex composed of the histone acetyltransferase 1 (Hat1) catalytic subunit and the Hat2 (rbap46) histone chaperone. Hat1 is predominantly localized in the nucleus as a member of a trimeric NuB4 complex containing Hat1, Hat2, and a histone H3-H4 specific histone chaperone called Hif1 (NASP). In addition to Hif1 and Hat2, Hat1 interacts with Asf1 (anti-silencing function 1), a histone chaperone that has been reported to be involved in both replication-dependent and -independent chromatin assembly. To elucidate the molecular roles of the Hif1 and Asf1 histone chaperones in HAT-B histone binding and acetyltransferase activity, we have characterized the stoichiometry and binding mode of Hif1 and Asf1 to HAT-B and the effect of this binding on the enzymatic activity of HAT-B. We find that Hif1 and Asf1 bind through different modes and independently to HAT-B, whereby Hif1 binds directly to Hat2, and Asf1 is only capable of interactions with HAT-B through contacts with histones H3-H4. We also demonstrate that HAT-B is significantly more active against an intact H3-H4 heterodimer over a histone H4 peptide, independent of either Hif1 or Asf1 binding. Mutational studies further demonstrate that HAT-B binding to the histone tail regions is not sufficient for this enhanced activity. Based on these data, we propose a model for HAT-B/histone chaperone assembly and acetylation of H3-H4 complexes.     

Induction by Fructose Force-Feeding of Histone H3 and H4 Acetylation at Their Lysine Residues around the Slc2a5 Gene and Its Expression in Mice

It has been reported that fructose force-feeding rapidly induced jejunal Slc2a5 gene expression in rodents. We demonstrate in this study that acetylation at lysine (K) 9 of histone H3 and acetylation at K5 and K16 of histone H4 were more enhanced in the promoter/enhancer to transcribed regions of the Slc2a5 gene in fructose force-fed mice than in glucose force-fed mice. However, fructose force-feeding did not induce acetylation at K14 of histone H3, or at K8 and K12 of histone H4 around the Slc2a5 gene. These results suggest that fructose force-feeding induced selective histone acetylation, particularly of H3 and H4, around the jejunal Slc2a5 gene in mice.     

组蛋白不同乙酰化位点突变对酵母细胞生长和Ssa3、Gal1基因表达的影响

组蛋白乙酰化对基因表达和细胞生长非常重要.为揭示组蛋白H3K14和H4K8的乙酰化修饰对不同条件下细胞生长和Ssa3、Gal1基因表达的重要性及二者功能差异.构建了H3K14、H4K8分别突变为精氨酸的单突变株S14、S8及二者同时突变的双突变株D814,并对其在正常、高温、咖啡因存在等条件下生长及Ssa3、Gal1表达进行比较.结果表明,所有突变株对咖啡因敏感性增加;D814对温度敏感,且在供试条件下其生长及Ssa3和Gal1激活均明显慢于野生型和单突变株;除半乳糖和葡萄糖为单一碳源,30℃时两单突变株差别不大外,其它条件下S8生长及Ssa3和Gal1激活均慢于S14.表明H3K14、H4K8乙酰化对细胞生长和适应不利环境非常重要,而且在对不利条件的快速适应方面,H4K8的乙酰化修饰可能更为重要.组蛋白突变株的表型缺陷是因该条件下细胞生存所必需的基因激活延迟所致.     

Regulation of the circadian rhythmic expression of Sglt1 in the mouse small intestine through histone acetylation and the mRNA elongation factor,BRD4-P-TEFb

Jejunal sodium/glucose co-transporter (Sglt1) displays circadian expression. The jejunum was collected every 4 h from mice, and we examined histone acetylation and binding of bromodomain-containing protein-4 (BRD4) around of the gene. Histone acetylation increased in the transcribed region of Sglt1 prior to induction of the gene. Furthermore, the binding of mRNA elongation factor around the gene showed circadian rhythm.     

组蛋白乙酰化在二烯丙基二硫诱导MGC803细胞分化中的作用

探讨二烯丙基二硫(DADS)诱导人胃癌MGC803细胞分化过程中组蛋白乙酰化状态的改变情况。运用形态学方法及成瘤实验观察DADS诱导MGC803细胞分化,应用Western印迹观察DADS诱导MGC803细胞分化与其调控细胞组蛋白乙酰化水平和相关p21WAF1的关系。形态学观察结果显示,30mg/LDADS处理MGC803细胞24h后,细胞异型性明显减少,且经裸鼠成瘤实验证实,处理后的细胞均未在裸鼠体内形成肿瘤;Western印迹显示,30mg/LDADS处理细胞12h后,其组蛋白H3乙酰化程度明显升高,与未处理组比较增加了38%(P<0.05);H4乙酰化程度无明显改变。用15、30、60mg/LDADS处理细胞12、24h后,p21WAF1均较对照组升高,以30mg/LDADS处理24h升高最显著。研究结果表明,DADS可诱导MGC803细胞分化,其作用可能与增加核组蛋白乙酰化水平及p21WAF1表达有关。     

The Structural Basis for Specific Recognition of H3K14 Acetylation by Sth1 in the RSC Chromatin Remodeling Complex

1. Download : Download high-res image (225KB)
2. Download : Download full-size image

     

Lessons from Yeast on Emerging Roles of the ATAD2 Protein Family in Gene Regulation and Genome Organization

ATAD2, a remarkably conserved, yet poorly characterized factor is found upregulated and associated with poor prognosis in a variety of independent cancers in human. Studies conducted on the yeast Saccharomyces cerevisiae ATAD2 homologue, Yta7, are now indicating that the members of this family may primarily be regulators of chromatin dynamics and that their action on gene expression could only be one facet of their general activity. In this review, we present an overview of the literature on Yta7 and discuss the possibility of translating these findings into other organisms to further define the involvement of ATAD2 and other members of its family in regulating chromatin structure and function both in normal and pathological situations.     

Dietary Resistant Starch Alters the Characteristics of Colonic Mucosa and Exerts a Protective Effect on Trinitrobenzene Sulfonic Acid-induced Colitis in Rats

The protective effect of a dietary high-amylose cornstarch (HAS) against trinitrobenzene sulfonic acid (TNBS)-induced colitis was examined in rats. Rats were fed a HAS-free basal diet or, a 15% or 30% HAS supplemented diet for 10 d, and then received intracolonic TNBS to induce colitis and fed the respective diets for a further 8 d. HAS ingestion significantly protected colonic injuries as evidenced by lower colonic myeloperoxidase activity. Rats fed the HAS diet showed greater cecal short-chain fatty acid (SCFA) production than those fed the basal diet. Further, just before TNBS administration, HAS ingestion dose-dependently increased fecal and cecal mucin contents, and protein and nucleic acid contents in the colonic mucosa. HAS ingestion also reduced colonic permeability. The protective effect of HAS ingestion on TNBS-induced colitis is perhaps exerted through alterations in colonic mucosa, possibly due to cecal SCFA production.