Profiling of sugar transporter genes in grapevine coping with water deficit

The profiling of grapevine (Vitis vinifera L.) genes under water deficit was specifically targeted to sugar transporters. Leaf water status was characterized by physiological parameters and soluble sugars content. The expression analysis provided evidence that VvHT1 hexose transporter gene was strongly down-regulated by the increased sugar content under mild water-deficit. The genes of monosaccharide transporter VvHT5, sucrose carrier VvSUC11, vacuolar invertase VvGIN2 and grape ASR (ABA, stress, ripening) were up-regulated under severe water stress. Their regulation in a drought-ABA signalling network and possible roles in complex interdependence between sugar subcellular partitioning and cell influx/efflux under Grapevine acclimation to dehydration are discussed.     

MicroRNA-7 arrests cell cycle in G1 phase by directly targeting CCNE1 in human hepatocellular carcinoma cells

Growing evidence has demonstrated that the aberrant expression of miRNA is a hallmark of malignancies, indicating the important roles of miRNA in the development and progression of cancer. MiR-7 is considered as a tumor suppressor miRNA in multiple types of cancer. However, the role of miR-7 in human hepatocellular carcinoma (HCC) and its underlying mechanism remain elusive. In this study, we found that overexpression of miR-7 arrested cell cycle at G1 to S transition in HCC. By combinational use of bioinformatic prediction, reporter assay, quantitative real-time PCR (qRT-PCR) and Western blot, we confirmed that CCNE1, an important mediator in G1/S transition is one of new direct target genes of miR-7. Further studies revealed that silencing of CCNE1 recapitulated the effects of miR-7 overexpression, whereas enforced expression of CCNE1 reversed the suppressive effects of miR-7 in cell cycle regulation. Finally, analysis of qRT-PCR showed a reciprocal relationship between miR-7 and CCNE1 in clinical cancer tissues and multiple types of tumor cell lines. These findings indicate that miR-7 exerts tumor-suppressive effects in hepatocarcinogenesis through the suppression of oncogene CCNE1 expression and suggest a therapeutic application of miR-7 in HCC.     

乳腺癌中雌激素受体α表达水平调节的分子机制

雌激素受体α(ERα)在乳腺癌的发生发展中扮演重要角色,因而ERα成为乳腺癌治疗的分子靶标。ERα的表达水平在乳腺癌患者中差异较大,即使同一患者,在乳腺癌的不同阶段也可能有很大的差别。乳腺癌内分泌治疗的疗效以及预后都与ERα表达水平密切相关。影响ERα表达水平的分子机制复杂,众多调节分子在染色质、转录、转录后、翻译和翻译后等水平参与ERα表达水平的调节。在染色质和转录水平,许多分子通过直接或间接地与ERα启动子的相互作用改变ERα的转录;在转录后/翻译水平,一些microRNA通过诱导ERαmRNA的降解和/或抑制其翻译降低ERα的水平;在翻译后水平,许多分子通过泛素-蛋白酶体途径调节ERα蛋白水平。文章从不同水平,对这些调节分子的调节机制进行简要综述。     

The Ras‐ERK pathway: Understanding site‐specific signaling provides hope of new anti‐tumor therapies

Recent discoveries have suggested the concept that intracellular signals are the sum of multiple, site‐specified subsignals, rather than single, homogeneous entities. In the context of cancer, searching for compounds that selectively block subsignals essential for tumor progression, but not those regulating “house‐keeping” functions, could help in producing drugs with reduced side effects compared to compounds that block signaling completely. The Ras‐ERK pathway has become a paradigm of how space can differentially shape signaling. Today, we know that Ras proteins are found in different plasma membrane microdomains and endomembranes. At these localizations, Ras is subject to site‐specific regulatory mechanisms, distinctively engaging effector pathways and switching‐on diverse genetic programs to generate different biological responses. The Ras effector pathway leading to ERKs activation is also under strict, space‐related regulatory processes. These findings may open a gate for aiming at the Ras‐ERK pathway in a spatially restricted fashion, in our quest for new anti‐tumor therapies.     

O-GlcNAc protein modification in plants: Evolution and function

The role in plants of posttranslational modification of proteins with O-linked N-acetylglucosamine and the evolution and function of O-GlcNAc transferases responsible for this modification are reviewed. Phylogenetic analysis of eukaryotic O-GlcNAc transferases (OGTs) leads us to propose that plants have two distinct OGTs, SEC- and SPY-like, that originated in prokaryotes. Animals and some fungi have a SEC-like enzyme while plants have both. Green algae and some members of the Apicomplexa and amoebozoa have the SPY-like enzyme. Interestingly the progenitor of the Apicomplexa lineage likely had a photosynthetic plastid that persists in a degenerated form in some species, raising the possibility that plant SPY-like OGTs are derived from a photosynthetic endosymbiont. OGTs have multiple tetratricopeptide repeats (TPRs) that within the SEC- and SPY-like classes exhibit evidence of strong selective pressure on specific repeats, suggesting that the function of these repeats is conserved. SPY-like and SEC-like OGTs have both unique and overlapping roles in the plant. The phenotypes of sec and spy single and double mutants indicate that O-GlcNAc modification is essential and that it affects diverse plant processes including response to hormones and environmental signals, circadian rhythms, development, intercellular transport and virus infection. The mechanistic details of how O-GlcNAc modification affects these processes are largely unknown. A major impediment to understanding this is the lack of knowledge of the identities of the modified proteins.