Crystal structure of the RNA demethylase ALKBH5 from zebrafish

ALKBH5, a member of AlkB family proteins, has been reported as a mammalian N⁶-methyladenosine (m⁶A) RNA demethylase. Here we report the crystal structure of zebrafish ALKBH5 (fALKBH5) with the resolution of 1.65 Å. Structural superimposition shows that fALKBH5 is comprised of a conserved jelly-roll motif. However, it possesses a loop that interferes potential binding of a duplex nucleic acid substrate, suggesting an important role in substrate selection. In addition, several active site residues are different between the two known m⁶A RNA demethylases, ALKBH5 and FTO, which may result in their slightly different pathways of m⁶A demethylation.     

Lnc-PFAR facilitates autophagy and exacerbates pancreatic fibrosis by reducing pre-miR-141 maturation in chronic pancreatitis

Chronic pancreatitis (CP) is described as progressive inflammatory fibrosis of pancreas, accompanied with irreversible impaired endocrine and exocrine insufficiency. Pancreatic stellate cells (PSCs) are widely distributed in the stroma of the pancreas and PSCs activation has been shown as one of the leading causes for pancreatic fibrosis. Our previous study has revealed that autophagy is dramatically activated in CP tissues, which facilitates PSCs activation and pancreatic fibrosis. Long non-coding RNAs (LncRNAs) have been recognized as crucial regulators for fibrosis-related diseases. LncRNAs interact with RNA binding protein or construct competitive endogenous RNA (ceRNA) hypothesis which elicited the fibrotic processes. Until now, the effects of lncRNAs on PSCs activation and pancreatic fibrosis have not been clearly explored. In this study, a novel lncRNA named Lnc-PFAR was found highly expressed in mouse and human CP tissues. Our data revealed that Lnc-PFAR facilitates PSCs activation and pancreatic fibrosis via RB1CC1-induced autophagy. Lnc-PFAR reduces miR-141 expression by suppressing pre-miR-141 maturation, which eventually upregulates the RB1CC1 and fibrosis-related indicators expression. Meanwhile, Lnc-PFAR enhanced PSCs activation and pancreatic fibrosis through trigging autophagy. Our study interrogates a novel lncRNA-induced mechanism in promoting the development of pancreatic fibrosis, and Lnc-PFAR is suggested to be a prospective therapeutic target in clinical scenarios.Subject terms: RNAi, Diagnostic markers, Chronic pancreatitis     

人脐带间充质干细胞微囊减轻小鼠急性肾损伤的研究

目的探讨人脐带间充质干细胞（MSCs）源性细胞外囊泡Oct-4 mRNA对受损的肾小管上皮细胞修复的作用及相关机制。 方法将培养的缺氧损伤肾小管上皮细胞置于含有人脐带MSCs细胞外囊泡及不同对照培养液的培养腔室玻片上孵育48?h,应用BrdU及TUNEL染色,检测各组细胞增殖或凋亡情况。将急性肾损伤模型小鼠分为4组：空白组、EVs组、Oct-4过表达组、Oct-4低敲组。并按照分组分别注射磷酸盐缓冲液（Vehicle）,人脐带MSCs细胞外囊泡（EVs）,过表达Oct-4基因的人脐带MSCs细胞外囊泡（EVs?+?Oct-4）及敲除Oct-4基因的人脐带MSCs外囊泡（EVs-Oct-4）,并在注射48?h及2周后采血测肌酐（Crea）及尿素氮（BUN）,了解肾功能变化;对各组上述处理后的肾组织应用TUNEL与增殖细胞核抗原表达量检测各组肾脏细胞凋亡与增殖情况;通过Masson染色检测了各组肾脏纤维化程度;通过PCR探索肾损伤后肾组织细胞Snail基因的表达变化。数据分析采用方差分析和SNK-q检验。 结果EVs?+ Oct-4处理缺氧的肾小管上皮细胞48?h后,TUNEL染色显示具有最少的凋亡细胞数（0~1）/?HPF,BrdU显示有最多的增殖细胞（7±2）/HPF。EVs,EV-Oct-4以及Vehicle对体外缺氧肾小管上皮细胞的上述作用依次减弱（P?相似文献   

植物生长发育和逆境响应中SR-like蛋白的研究进展

同一基因pre-mRNA经可变剪接(alternative splicing, AS)后能够产生不同的转录本,使得编码的蛋白在细胞中的定位、稳定性和翻译后修饰的功能发生改变,进而增强应答发育及环境胁迫的能力,富含丝氨酸-精氨酸蛋白(serine/arginine-rich proteins, SR proteins/SR)是决定可变剪接效率和准确性的一个重要剪接因子家族。该文在简要介绍SR蛋白概念、分类的基础上,首次系统综述了植物特有的SR蛋白亚家族SR-like(SR45/45a)结构特点、成员构成、亚细胞定位和转录调控功能,尤其是对于非生物胁迫应答过程中相关基因可变剪接的调控机制进行了阐述,并展望了未来植物SR-like可能的前景方向和研究内容。     

Three dimensional de novo micro bone marrow and its versatile application in drug screening and regenerative medicine

The finding that bone marrow hosts several types of multipotent stem cell has prompted extensive research aimed at regenerating organs and building models to elucidate the mechanisms of diseases. Conventional research depends on the use of two-dimensional (2D) bone marrow systems, which imposes several obstacles. The development of 3D bone marrow systems with appropriate molecules and materials however, is now showing promising results. In this review, we discuss the advantages of 3D bone marrow systems over 2D systems and then point out various factors that can enhance the 3D systems. The intensive research on 3D bone marrow systems has revealed multiple important clinical applications including disease modeling, drug screening, regenerative medicine, etc. We also discuss some possible future directions in the 3D bone marrow research field.     

Hypoxic preconditioning advances CXCR4 and CXCR7 expression by activating HIF-1α in MSCs

Recent evidence indicated that sublethal hypoxic preconditioning (HP) of bone marrow-derived mesenchymal stem cells (MSCs) before transplantation could ameliorate their capacity to survive and engraft in the target tissue through yet undefined mechanisms. In this study, we demonstrated that HP (3% oxygen) induced the high expression of both chemokine stromal-derived factor-1 (SDF-1) receptors, CXCR4 and CXCR7, in MSCs. HP also improved in vitro migration, adhesion and survival of MSCs. Although SDF-1-induced migration of HP-MSCs was only abolished by an anti-CXCR4 antibody, both CXCR4 and CXCR7 were responsible for elevated adhesion of HP-MSCs. Moreover, CXCR7 but not CXCR4 was essential for the resistance to oxidative stress of HP-MSC. In addition, HP also evoked an increase in expression of hypoxia-inducible factor-1 (HIF-1α) and phosphorylation of Akt. The chemical inducers of HIF-1α, desferrioxamine (DFX) and cobalt chloride (CoCl₂), induced upregulation of CXCR4 and CXCR7 expression in MSCs under normoxic conditions. Contrarily, blockade of HIF-1α by siRNA and inhibition of Akt by either wortmannin or LY294002 abrogated upregulation of HP-induced CXCR4 and CXCR7 in MSCs. Collectively, these findings provide evidence for a crucial role of PI3K/Akt-HIF-1α-CXCR4/CXCR7 pathway on enhanced migration, adhesion and survival of HP-MSCs in vitro.