ABSTRACT
The phytohormone cytokinin has various roles in plant development, including meristem maintenance, vascular differentiation, leaf senescence, and regeneration. Prior investigations have revealed that cytokinin acts via a phosphorelay similar to the two-component system by which bacteria sense and respond to external stimuli. The eventual targets of this phosphorelay are type-B ARABIDOPSIS RESPONSE REGULATORS (B-ARRs), containing the conserved N-terminal receiver domain (RD), middle DNA binding domain (DBD), and C-terminal transactivation domain. While it has been established for two decades that the phosphoryl transfer from a specific histidyl residue in ARABIDOPSIS HIS PHOSPHOTRANSFER PROTEINS (AHPs) to an aspartyl residue in the RD of B-ARRs results in a rapid transcriptional response to cytokinin, the underlying molecular basis remains unclear. In this work, we determine the crystal structures of the RD-DBD of ARR1 (ARR1RD-DBD) as well as the ARR1DBD-DNA complex from Arabidopsis. Analyses of the ARR1DBD-DNA complex have revealed the structural basis for sequence-specific recognition of the GAT trinucleotide by ARR1. In particular, comparing the ARR1RD-DBD and ARR1DBD-DNA structures reveals that unphosphorylated ARR1RD-DBD exists in a closed conformation with extensive contacts between the RD and DBD. In vitro and vivo functional assays have further suggested that phosphorylation of the RD weakens its interaction with DBD, subsequently permits the DNA binding capacity of DBD, and promotes the transcriptional activity of ARR1. Our findings thus provide mechanistic insights into phosphorelay activation of gene transcription in response to cytokinin.
Subject(s)
Arabidopsis , Cytokinins , Transcriptional Activation , Arabidopsis/genetics , Plant Growth Regulators , DNAABSTRACT
Exosome are nano-scale vesicles with a phospholipid bilayer membrane structure. They are widely distributed in body fluids such as serum, urine, and saliva, containing various biologically active substances such as RNA, DNA fragment and protein. Exosomes contain miRNAs called exosomal-derived miRNAs. Gastrointestinal tumors are one of the common malignant tumors. Effective screening and early diagnosis are clinical priorities and difficulties. Exosome-derived miRNAs in human circulation can be used as potential biomarkers for early diagnosis of digestive tract tumors. This article reviews the concepts and biological characteristics of exosomal-derived miRNAs, the detection of exosome-derived miRNAs and the relationship between exosome-derived miRNAs and digestive tract tumors.
ABSTRACT
Circular RNA (circRNA) is a class of endogenous non-coding RNA molecules with a stable closed loop structure formed by reverse splicing. It is more conserved and stable than linear RNA and involves cell development, proliferation, differentiation and apoptosis. Long-term and large-scale studies show the dysregulation of circRNA is associated with the risk of invasion, staging, metastasis, and postoperative recurrence of gastric cancer. This paper reviews the structure, classification, function of circRNA and its clinical significance in gastric cancer.
ABSTRACT
Background Some drugs with inhibitory effect on the proliferation of lens epithelial cells have a limiting application in clinic because of their adverse response.To screen the effective and less side-effect drug for supressing LECs growth is very inportant for the prevention and treatment of after cataract.Objective This study was to explore the effects of docetaxel on LECs growth and compare its role with epirubicin hydrochloride,pirarubicin hydrochloTide and rahitrexed.Methotis Immortalized human LECs line (SRA01/04) were cultured and passaged.Different concentrations of docetaxel,epirubicin hydrochloride,pirarubicin hydrochloride and rahitrexed were added into the medium respectively for 24.48 and 72 hours.The proliferation of LECs was detect by M1Yr.Flow cytometry analysis Was used to analyze the influence of different concentrations of docetaxel on cellular cycle at 48 hours after addition of docetaxel,and Annexin V-FITC/PI marking method was used to assesse the apoptosis of LECs under the action of docetaxel.Expression of bcl-2 protein in LECs Was evaluated by Westeru blot. Result The growth rate of LECs Wag 100%in 8-519 pmol/L doeetaxel groups with the normal cell shape.Majority of abnormal cells and low growth rate were found in 66 nmoVL docetaxel group at 48 and 72 hours.The IC50 of docetaxel was lowest in 48 and 72 hours in docetaxel group in comparison to epirubicin hydrochloride and pirarubicin hydrochloride. However,no evident inhibition on LECs growth in 23.22-523.56 μmol/L of raltitrexed.At 48 hours,the percentage of LECs in G2/M phase increased as the asccnte of concentration of docetaxel,showing a significant difference among 4 groups(F=2633.05,P＜0.01).The percentage of early apoptotic cells increased to 22.4%(χ2=20.00,P＜0.01) and 27.9%(χ2=42.68,P＜0.01)from normal control 3.1% at 48 hours after LECs exposed to 8.3 nmol/L and 266 nmol/L docetaxe.The expression of bcl-2 protein in LECs was obviously weakened after addition of docetaxel,especially 8.3 nmol/L docetaxel group. Conclusion Docetaxel,epirubicin hydrochloride and pirarubicin hydrochloride can inhibit the proliferation of human LECs in vitro.But there is no supression on LECs growth inraltitrexed.Docetaxel is proved to have a strongly arrested effect on the proliferation of LECs in comparison with epirubicin hydrochloride and pirarubicin hydrochloride and play its role at concentration-and time-dependent manner.