Dual activities of ACC synthase: Novel clues regarding the molecular evolution of ACS genes.

Ethylene plays profound roles in plant development. The rate-limiting enzyme of ethylene biosynthesis is 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS), which is generally believed to be a single-activity enzyme evolving from aspartate aminotransferases. Here, we demonstrate that, in addition to catalyzing the conversion of S-adenosyl-methionine to the ethylene precursor ACC, genuine ACSs widely have Cß-S lyase activity. Two N-terminal motifs, including a glutamine residue, are essential for conferring ACS activity to ACS-like proteins. Motif and activity analyses of ACS-like proteins from plants at different evolutionary stages suggest that the ACC-dependent pathway is uniquely developed in seed plants. A putative catalytic mechanism for the dual activities of ACSs is proposed on the basis of the crystal structure and biochemical data. These findings not only expand our current understanding of ACS functions but also provide novel insights into the evolutionary origin of ACS genes.

MicroRNA-664-5p promotes myoblast proliferation and inhibits myoblast differentiation by targeting serum response factor and Wnt1.

MicroRNAs (miRNAs) are noncoding RNAs that regulate gene expression at the post-transcriptional level and are involved in the regulation of the formation, maintenance, and function of skeletal muscle. Using miRNA sequencing and bioinformatics analysis, we previously found that the miRNA miR-664-5p is significantly differentially expressed in longissimus dorsi muscles of Rongchang pigs. However, the molecular mechanism by which miR-664-5p regulates myogenesis remains unclear. In this study, using flow cytometry, 5-ethynyl-2'-deoxyuridine staining, and cell count and immunofluorescent assays, we found that cell-transfected miR-664-5p mimics greatly promoted proliferation of C2C12 mouse myoblasts by increasing the proportion of cells in the S- and G2-phases and up-regulating the expression of cell cycle genes. Moreover, miR-664-5p inhibited myoblast differentiation by down-regulating myogenic gene expression. In contrast, miR-664-5p inhibitor repressed myoblast proliferation and promoted myoblast differentiation. Mechanistically, using dual-luciferase reporter gene experiments, we demonstrated that miR-664-5p directly targets the 3'-UTR of serum response factor (SRF) and Wnt1 mRNAs. We also observed that miR-664-5p inhibits both mRNA and protein levels of SRF and Wnt1 during myoblast proliferation and myogenic differentiation, respectively. Furthermore, the activating effect of miR-664-5p on myoblast proliferation was attenuated by SRF overexpression, and miR-664-5p repressed myogenic differentiation by diminishing the accumulation of nuclear ß-catenin. Of note, miR-664-5p's inhibitory effect on myogenic differentiation was abrogated by treatment with Wnt1 protein, the key activator of the Wnt/ß-catenin signaling pathway. Collectively, our findings suggest that miR-664-5p controls SRF and canonical Wnt/ß-catenin signaling pathways in myogenesis.

Long noncoding RNA: multiple players in gene expression.

Previously considered as a component of transcriptional noise, long noncoding RNAs (lncRNAs) were neglected as a therapeutic target, however, recently increasing evidence has shown that lncRNAs can participate in numerous biological processes involved in genetic regulation including epigenetic, transcriptional, and post-transcriptional regulation. In this review, we discuss the fundamental functions of lncRNAs at different regulatory levels and their roles in metabolic balance. Typical examples are introduced to illustrate their diverse molecular mechanisms. The comprehensive investigation and identification of key lncRNAs will not only contribute to insights into diseases, such as breast cancer and type II diabetes, but also provide promising therapeutic targets for related diseases. [BMB Reports 2018; 51(6): 280-289].

Adiponectin AS lncRNA inhibits adipogenesis by transferring from nucleus to cytoplasm and attenuating Adiponectin mRNA translation.

Adiponectin (AdipoQ) is an adipocyte-derived hormone with positive function on systemic glucose and lipid metabolism. Long noncoding RNA (lncRNA) is emerging as a vital regulator of adipogenesis. However, AdipoQ-related lncRNAs in lipid metabolism have not been explored. Here, AdipoQ antisense (AS) lncRNA was first identified, and we further found that it inhibited adipogenesis. The half-life of AdipoQ AS lncRNA was 10 h, whereas that of AdipoQ mRNA was 4 h. During adipogenic differentiation, AdipoQ AS lncRNA translocated from nucleus to cytoplasm. AdipoQ AS lncRNA and AdipoQ mRNA formed an RNA duplex. Moreover, AdipoQ AS lncRNA delivered via injection of adenovirus expressing AdipoQ AS lncRNA decreases white adipose tissue (WAT), brown adipose tissue (BAT) and liver triglycerides (TG) in mice consuming a high fat diet (HFD). Interestingly, the non-overlapping region of AdipoQ AS lncRNA improved serum glucose tolerance and insulin sensitivity in HFD mice, but not AdipoQ AS lncRNA. In conclusion, AdipoQ AS lncRNA transfer from nucleus to cytoplasm inhibits adipogenesis through formation of an AdipoQ AS lncRNA/AdipoQ mRNA duplex to suppress the translation of AdipoQ mRNA. Taken together, we suggest that AdipoQ AS lncRNA is a novel therapeutic target for obesity-related metabolic diseases.

CTRP6 Regulates Porcine Adipocyte Proliferation and Differentiation by the AdipoR1/MAPK Signaling Pathway.

Intramuscular fat (IMF) and subcutaneous fat (SCF), which are modulated by adipogenesis of intramuscular and subcutaneous adipocytes, play key roles in pork quality. C1q/tumor necrosis factor-related protein 6 (CTRP6), an adipokine, plays an important role in the differentiation of 3T3-L1 cells. However, the effect and regulatory mechanisms of CTRP6 on porcine adipogenesis, and whether CTRP6 has the same effect on intramuscular and subcutaneous adipocytes, are still unknown. Here, we found that CTRP6 significantly inhibited both adipocyte proliferation assessed by proliferative marker expression, but CTRP6 decreased the proliferation rate of intramuscular adipocytes (IM) to a greater extent than subcutaneous adipocytes (SC). Moreover, CTRP6 promoted the activity of the p38 signaling pathway during the proliferation of both cell types. Nevertheless, in subcutaneous adipocytes, CTRP6 also influenced the phosphorylation of extracellular regulated protein kinases1/2 (p-Erk1/2), but not in intramuscular adipocytes. Additionally, during the differentiation of intramuscular and subcutaneous adipocytes, CTRP6 increased adipogenic genes expression and the level of p-p38, while it decreased the activity of p-Erk1/2. Interestingly, the effect of CTRP6 shRNA or CTRP6 recombinant protein was attenuated by U0126 (a special p-Erk inhibitor) or SB203580 (a special p-p38 inhibitor) in adipocytes. By target gene prediction and experimental validation, we demonstrated that CTRP6 may be a target of miR-29a in porcine adipocytes. Moreover, AdipoR1was identified as a receptor of CTRP6 in intramuscular adipocytes, but not in subcutaneous adipocytes. On the basis of the above findings, we suggest that CTRP6 was the target gene of miR-29a, inhibited intramuscular and subcutaneous adipocyte proliferation, but promoted differentiation by the mitogen-activated protein kinase (MAPK) signaling pathway. These findings indicate that CTRP6 played an essentially regulatory role in fat development.