ik3-1/Cables is a substrate for cyclin-dependent kinase 3 (cdk 3).

p70ik3-1 (a 70-kDa protein) contains a cyclin box, and binds to p35cdk3 in vivo and in vitro [Matsuoka, M., Matsuura, Y., Semba, K. & Nishimoto, I. (2000) Biochem. Biophys. Res. Commun. 273, 442-447]. In spite of its structural similarity to cyclins, p70ik3-1 does not activate cyclin-dependent kinase 3 (cdk3)-mediated phosphorylation of pRb, histone H1, or the C-terminal domain of RNA polymerase II. Here, we report that Ser274 of p70ik3-1 is phosphorylated by cdk2 or cdk3 bound to cyclin A and to cyclin E in vitro. We also found that in COS7 cells in which cyclin E and cdk3 were ectopically overexpressed, the phosphorylation level of Ser274 in coexpressed p70ik3-1 is upregulated. We therefore conclude that p70ik3-1 is a substrate for cdk3-mediated phosphorylation.     

Enzymatic RNA synthesis and RNase P

TransferRNA recognition was used as leit-motiv in the illustration of possible links between a hypothetical primordial RNA world and the contemporary DNA world. In an RNA world, proto-tRNA could have functioned as replication origin and as primitive telomere. Possibly, this primitive structure is preserved in a universal substrate for modern tRNA-specific enzymes. The combination of acceptor stem and T arm (plus a linker) was finally revealed as sufficient for the recognition by prokaryotic and eukaryotic RNase P, as well as other tRNA enzymes. In modern life forms, a tRNA-like element in viral RNAs still serves as replication origin, and furthermore, the recognition of similar structures as cryptic promoters is universally conserved for template-dependent RNA polymerases. Another common property of modern polymerases is their high, but clearly limited and condition-dependent substrate specificity. Very likely, also substrate recognition by primitive polymerases was not more stringent, and this lead to the ocurrence of mixed nucleic acids as intermediates in the transition from genomic RNA to contemporary genomic DNA.Abbreviations (d)NTP (deoxy)nucleoside triphosphate - nt nucleotide(s)     

LncRNA MEG3 regulates breast cancer proliferation and apoptosis through miR-141-3p/RBMS3 axis

Maternally expressed 3 (MEG3) and RNA binding motif single stranded interacting protein 3 (RBMS3) are abnormally expressed in breast cancer susceptibility genes (BRCA), but the mechanism of the two in breast cancer (BC) is unclear. By performing in vivo and in vitro experiments, we found that MEG3 and RBMS3 were low-expressed, negatively correlated with high-expressed miR-141-3p, were positively correlated with each other in BC. MEG3 targeted miR-141-3p, and miR-141-3p targeted RBMS3. MEG3, which was mainly distributed in BC cytoplasm, could down-regulate miR-141-3p and up-regulate RBMS3, and reverse effect of miR-141-3p on related gene expressions and on promoting cancer development. Overexpressed MEG3 inhibited growth of xenografts, promoted cell apoptosis via regulating apoptosis related factors, and up-regulated RBMS3 expression but down-regulated miR-141-3p. The findings of this study showed that MEG3 inhibited proliferation and promoted apoptosis of BC cells through the miR-141-3p/RBMS3 axis, and MEG3 inhibited growth of xenografts through miR-141-3p.     

The RNA recognition motif of yeast translation initiation factor Tif3/eIF4B is required but not sufficient for RNA strand-exchange and translational activity.

The Saccharomyces cerevisiae TIF3 gene encodes a 436-amino acid (aa) protein that is the yeast homologue of mammalian translation Initiation factor eIF4B. Tif3p can be divided into three parts, the N-terminal region with an RNA recognition motif (RRM) (aa 1-182), followed in the middle part by a sevenfold repeat of 26 amino acids rich in basic and acidic residues (as 183-350), and a C-terminal region without homology to any known sequence (aa 351-436). We have analyzed several Tif3 proteins with deletions at their N and C termini for their ability (1) to complement a tif3delta strain in vivo, (2) to stimulate Tif3-dependent translation extracts, (3) to bind to single-stranded RNA, and (4) to catalyze RNA strand-exchange in vitro. Here we report that yeast Tif3/eIF4B contains at least two RNA binding domains able to bind to single-stranded RNA. One is located in the N-terminal region of the protein carrying the RRM, the other in the C-terminal two-thirds region of Tif3p. The RRM-containing domain and three of the seven repeat motifs are essential for RNA strand-exchange activity of Tif3p and translation in vitro and for complementation of a tif3delta strain, suggesting an important role for RNA strand-exchange activity in translation.     

lncRNA SNHG3 facilitates acute myeloid leukemia cell growth via the regulation of miR-758-3p/SRGN axis

Small nucleolar RNA host gene 3 (SNHG3) is a newly identified long non-coding RNA whose dysregulation has been reported in several cancers. However, the details about clinical significances and biological functions of SNHG3 on acute myeloid leukemia (AML) remain covered. In this study, we revealed increased SNHG3 expression in AML samples and cells and its high potential as a prognostic biomarker for AML patients. Likewise, serglycin (SRGN), which plays an important role in granule-mediated apoptosis, was previously verified to be upregulated in AML and confirmed again by the present study, and its upregulation predicted poor outcomes in AML. Furthermore, knockdown of SNHG3 or SRGN inhibited cell proliferation and induced cell apoptosis. Besides, silencing SNHG3 noticeably decreased the expression of SRGN in AML cells. Moreover, we uncovered that SNHG3 modulated SRGN expression by competitively binding with miR-758-3p. Importantly, both miR-758-3p suppression and SRGN overexpression could mitigate the inhibitory effects of SNHG3 depletion on AML cell growth. Intriguingly, the higher SRGN expression in AML samples with a higher SNHG3 level exhibited an enhanced Ki67 level but a reduced caspase 3 level. To sum up, SNHG3 elicits a growth-promoting function in AML via sponging miR-758-3p to regulate SRGN expression, providing a new therapeutic road for AML patients.     

Upregulation of long noncoding TNFSF10 contributes to osteoarthritis progression through the miR-376-3p/FGFR1 axis

Osteoarthritis (OA) is a common joint disease with high morbidity, but there is still no definitive treatment for it. Long noncoding RNAs (lncRNAs) have been confirmed to play key roles in OA progression. This work was done to investigate the roles and action mechanism of lncRNA TNFSF10 in OA. The messenger RNA levels of TNFSF10 in articular cartilage samples from patients or chondrocytes were detected by Quantitative real-time PCR assay (qRT-PCR). The effects of TNFSF10 on chondrocytes were evaluated on the basis of cell growth, apoptosis, and inflammation. Then, the interaction between TNFSF10 and miR-376-3p was explored by dual-luciferase reporter test, RNA-binding protein immunoprecipitation, and RNA pull-down assay. Finally, various cell experiments, Western blot analysis, and qRT-PCR were performed to study the interaction among TNFSF10, miR-376-3p, and fibroblast growth factor receptor 1 (FGFR1). It was found that TNFSF10 was upregulated in OA cartilages and stimulated cell proliferation, antiapoptosis, and inflammation for chondrocytes. In addition, TNFSF10 acted as a competing endogenous RNA to downregulate miR-376-3p, and the influence of TNFSF10 on chondrocytes was partly reversed by miR-376-3p. Moreover, FGFR1, as a target of miR-376-3p, had reversal functions on the outcomes mediated by miR-376-3p. The further analysis displayed that there was a negative relationship between TNFSF10 and miR-376-3p as well as miR-376-3p and FGFR1, while FGFR1 was positively related with TNFSF10. Altogether, TNFSF10 overexpression probably stimulated proliferation and inflammation, and inhibited apoptosis by regulating the miR-376-3p/FGFR1 axis, implying that its increase contributed to OA progression. Our study provided a new potential biomarker or therapeutic target-TNFSF10, which was helpful to develop an efficient approach to cure OA.     

LncRNA TTN-AS1 drives invasion and migration of lung adenocarcinoma cells via modulation of miR-4677-3p/ZEB1 axis

Lung adenocarcinoma is the most prevalent type of lung cancer with a high incidence and mortality worldwide. Metastasis is the major cause of high death rate in lung cancer and the potential mechanism of lung adenocarcinoma metastasis remains indistinct. Emerging investigations have demonstrated that long noncoding RNA is a kind of non–protein coding RNA and plays a critical role in cancer progression and metastasis. TTN antisense RNA 1 (TTN-AS1) has been reported to promote cell growth and metastasis in cancer. However, the function of TTN-AS1 in lung adenocarcinoma is still to be illustrated. In this study, we observed that TTN-AS1 was upregulated in tissues and cells of lung adenocarcinoma and associated with poor overall survival. TTN-AS1 promoted cell proliferation, migration, invasion, and epithelial-mesenchymal transition in lung cancer. TTN-AS1 directly bound with miR-4677-3p and negatively regulated miR-4677-3p. MiR-4677-3p rescued the inhibitive impacts of TTN-AS1 knockdown on lung adenocarcinoma. Furthermore, zinc finger E-box binding homeobox 1 (ZEB1) was the target of miR-4677-3p, and TTN-AS1 modulated ZEB1 by competing for miR-4677-3p. TTN-AS1 drove the invasion and migration of lung adenocarcinoma cells by targeting the miR-4677-3p/ZEB1 axis. To sum up, our study offers insights into the mechanism of TTN-AS1 in lung adenocarcinoma metastasis and targeting the TTN-AS1/miR-4677-3p/ZEB1 axis may be the potential innovate therapeutic strategy for the patients with lung adenocarcinoma.     

Deep Sequencing of RNA from Three Different Extracellular Vesicle (EV) Subtypes Released from the Human LIM1863 Colon Cancer Cell Line Uncovers Distinct Mirna-Enrichment Signatures

Secreted microRNAs (miRNAs) enclosed within extracellular vesicles (EVs) play a pivotal role in intercellular communication by regulating recipient cell gene expression and affecting target cell function. Here, we report the isolation of three distinct EV subtypes from the human colon carcinoma cell line LIM1863 – shed microvesicles (sMVs) and two exosome populations (immunoaffinity isolated A33-exosomes and EpCAM-exosomes). Deep sequencing of miRNA libraries prepared from parental LIM1863 cells/derived EV subtype RNA yielded 254 miRNA identifications, of which 63 are selectively enriched in the EVs - miR-19a/b-3p, miR-378a/c/d, and miR-577 and members of the let-7 and miR-8 families being the most prominent. Let-7a-3p*, let-7f-1-3p*, miR-451a, miR-574-5p*, miR-4454 and miR-7641 are common to all EV subtypes, and 6 miRNAs (miR-320a/b/c/d, miR-221-3p, and miR-200c-3p) discern LIM1863 exosomes from sMVs; miR-98-5p was selectively represented only in sMVs. Notably, A33-Exos contained the largest number (32) of exclusively-enriched miRNAs; 14 of these miRNAs have not been reported in the context of CRC tissue/biofluid analyses and warrant further examination as potential diagnostic markers of CRC. Surprisingly, miRNA passenger strands (star miRNAs) for miR-3613-3p*, -362-3p*, -625-3p*, -6842-3p* were the dominant strand in A33-Exos, the converse to that observed in parental cells. This finding suggests miRNA biogenesis may be interlinked with endosomal/exosomal processing.     

Long non-coding RNA DANCR modulates osteogenic differentiation by regulating the miR-1301-3p/PROX1 axis

The balance of osteoblasts and marrow adipocytes from bone marrow mesenchymal stem cells (BM-MSCs) maintains bone health. Under aging or other pathological stimuli, BM-MSCs will preferentially differentiate into marrow adipocytes and reduce osteoblasts, leading to osteoporosis. Long non-coding RNA differentiation antagonizing non-protein coding RNA (DANCR) participates in the osteogenic differentiation of human BM-MSCs, but the mechanism by which DANCR regulates the osteogenic differentiation of human BM-MSCs has not been fully explained. We observed that DANCR and prospero homeobox 1 (PROX1) were downregulated during osteogenic differentiation of human BM-MSCs, while miR-1301-3p had an opposite trend. DANCR overexpression decreased the levels of alkaline phosphatase, RUNX2, osteocalcin, Osterix in BM-MSCs after osteogenic induction, but DANCR silencing had the opposite result. Moreover, DANCR sponged miR-1301-3p to regulate PROX1 expression. miR-1301-3p overexpression reversed the suppressive role of DANCR elevation on the osteogenic differentiation of human BM-MSCs. Also, PROX1 elevation abolished the promoting role of miR-1301-3p overexpression on the osteogenic differentiation of human BM-MSCs. In conclusion, DANCR suppressed the osteogenic differentiation of human BM-MSCs through the miR-1301-3p/PROX1 axis, offering a novel mechanism by which DANCR is responsible for the osteogenic differentiation of human BM-MSCs.

     

circ-016910 sponges miR-574-5p to regulate cell physiology and milk synthesis via MAPK and PI3K/AKT–mTOR pathways in GMECs

Incremental proofs demonstrate that miRNAs, the essential regulators of gene expression, are implicated in various biological procedures, including mammary development and milk synthesis. Here, the role of miR-574-5p in milk synthesis, apoptosis, and proliferation of goat mammary epithelial cells (GMECs) are explored without precedent, and the molecular mechanisms for the impacts are elucidated. Small RNA libraries were constructed using GMECs transfected with miR-574-5p mimics and negative control followed by sequencing via Solexa technology. Overall, 332 genes were distinguishingly expressed entre two libraries, with 74 genes upregulated and 258 genes downregulated. This approach revealed mitogen-activated protein kinase kinase kinase 9 (MAP3K9), an upstream activator of MAPK signaling, as a differentially expressed unigene. miR-574-5p targeted seed sequences of the MAP3K9 3′-untranslated region and suppressed its messenger RNA (mRNA) and protein levels, correspondingly. GMECs with miR-574-5p overexpression and MAP3K9 inhibition showed increased cell apoptosis and decreased cell proliferation resulting from sustained suppression of MAPK pathways, while MAP3K9 elevation manifested the opposite results. miR-574-5p repressed the phosphorylation of members of protein kinase B (AKT)–mammalian target of rapamycin pathway via downregulating MAP3K9 and AKT3, resulting in reducing the secretion of β-casein and triglycerides in GMECs. Finally, according to the constructed circular RNA (circRNA) libraries and bioinformatics prediction approach, we selected circ-016910 and found it acted as a sponge for miR-574-5p and blocked its relevant behaviors to undertake biological effects in GMECs. The circRNA–miRNA–mRNA network facilitates further probes on the function of miR-574-5p in mammary development and milk synthesis.