Circular RNA: The evolving potential in the disease world

Circular RNAs(circRNAs),a new star of noncoding RNAs,are a group of endogenous RNAs that form a covalently closed circle and occur widely in the mammalian genome.Most circRNAs are conserved throughout species and fre-quently show stage-specific expression during various stages of tissue develop-ment.CircRNAs were a mystery discovery,as they were initially believed to be a product of splicing errors;however,subsequent research has shown that ci-rcRNAs can perform various functions and help in the regulation of splicing and transcription,including playing a role as microRNA(miRNA)sponges.With the application of high throughput next-generation technologies,circRNA hotspots were discovered.There are emerging indications that explain the association of circRNAs with human diseases,like cancers,developmental disorders,and in-flammation,and circRNAs may be a new potential biomarker for the diagnosis and treatment outcome of various diseases,including cancer.After the discoveries of miRNAs and long noncoding RNAs,circRNAs are now acting as a novel re-search entity of interest in the field of RNA disease biology.In this review,we aim to focus on major updates on the biogeny and metabolism of circRNAs,along with their possible/established roles in major human diseases.

DDAH1-V3 transcript might act as miR-21 sponge to maintain balance of DDAH1-V1 in cultured HUVECs

OBJECTIVE To investigate whether micro RNA(mi RNA)mi R-21 regulates dimethylarginine dimethylaminohydrolase 1(DDAH1)expression through binding 3′-UTR regiondirectly in human umbilical venous endothelial cells(HUVECs)and to explore whether DDAH1-V2/V3 transcripts can function as micro RNA sponge,thereby modulating DDAH1-V1 expression.METHODS The DDAH13′-UTR containing mi R-21 recognizing sequence was cloned into Pmir GLO dual-luciferase mi RNA target expression plasmid to construct PmirGLO-mi R-21.The plasmid and mi R-21(at concentrations of 25,50,100 nmol·L-1,respectively)or negative control(100 nmol·L-1)were co-transfected into HUVECs,luciferase activity was detected at 24 h.HUVECs were incubated with 2μg·m L-1actinomycin D for the indicated time after mi R-21(25 nmol.L-1)transfection,half-lives of DDAH1 m RNA were determined.HUVECs were transfected with Pmir GLO-mi R-21 alone or co-transfected with mi R-21 for 24 h,DDAH1 transcripts m RNA and DDAH1protein expression were determined.RESULTS Mi R-21decreased luciferase activity of Pmir GLO-mi R-21 in a dose-dependent manner(P<0.05 for 25 nmol·L-1mi R-21,P<0.01 for 50 nmol·L-1and 100 nmol·L-1mi R-21),and mi R-21 inhibitor increased reporter activity of PmirGLO-mi R-21 and m RNA expression of all DDAH1 three transcript variants significantly(P<0.05,respectively).The degree of increase in endogenous DDAH1 m RNA expression by mi R-21 inhibitor was more obvious for DDAH1-V3.Overexpression of mi R-21 decreased m RNA expression and m RNA half-life time of all DDAH1 transcripts significantly(P<0.05),and DDAH1-V2 displayed significantly decreased half-life time than DDAH1-V1and-V3 with or without mi R-21 transfection(P<0.05,respectively).Mi R-21(100 nmol·L-1)decreased DDAH1protein expression significantly(P<0.05),which was reversed by Pmir GLO-mi R-21 transfection(P<0.05).Transfection of Pmir GLO-mi R-21 alone increased intracellular mi R-21 expression by approximately 5.6-fold,but only showed a trend of increase in DDAH1 protein expression.CONCLUSION Our results confirmed DDAH13′-UTR as a target for mi R-21,and endogenous mi R-21showed increased inhibitory effect on DDAH1-V3 transcript.DDAH1 3′-UTR,especially for DDAH1-V3,may function as mi R-21 sponge to regulate DDAH1 protein expression.Modulation of mi R-21-DDAH1 interaction may provide a new approach for tackling cardiovascular diseases.

Functions of Circular RNAs in the Research of Reproductive and Developmental Medicine

Circular RNAs(circRNAs)represent a mysterious class of noncoding RNAs that are generated by the circularization of exons or introns and characterized as being highly stable and abundant.Although circRNAs have been studied for several decades,our knowledge of these molecules remains limited.With the development of innovative bioinformatic tools and sequencing methods,comprehensive studies of circRNAs are now available in the literature.There is emerging evidence to show that circRNAs play roles in the regulation of gene expression.In this review,several primary potential functions of circRNAs are summarized;these include binding to microRNA/RNA-binding proteins,inhibiting/promoting messenger RNA translation,and their own translation.

Long non-coding RNAs regulation of therapeutic resistance

Non-protein coding RNAs have emerged as a regulator of cell signaling and cancer progression through regulation of cell proliferation,metastatic burden,and cancer stem cell capacity.A subtype of non-protein coding RNA is long non-protein coding RNA(lncRNA).Besides their aforementioned roles in cancer cell biology,dysregulation of lncRNAs contribute to resistance to therapeutic treatments.A couple of important therapeutic classes are chemotherapy and targeted/hormone therapies.This review highlights the variety of malignancies affected by lncRNA dysregulation and the underlying mechanism causing therapeutic resistance.