Centromeric Non-coding Transcription: Opening the Black Box of Chromosomal Instability?

LncRNA EWSAT1 Promotes Colorectal Cancer Progression Through Sponging miR-326 to Modulate FBXL20 Expression

BACKGROUND

Ewing sarcoma-associated transcript 1 (EWSAT1) has been reported to be a pivotal modulator in a series of cancers. However, the function of EWSAT1 in colorectal cancer (CRC) has not been elaborated. This study aimed to explore the role of EWSAT1 in CRC progression and the underlying mechanisms.

METHODS

The expression patterns of EWSAT1, miR-326 and FBXL20 were examined by qCRCR. Si-EWSAT1 was transfected to study the effects of EWSAT1 on cell proliferation and metastasis. Rescue experiments were performed to investigate the underlying mechanisms in vitro. Xenograft models were used to evaluate the role of EWSAT1 in vivo.

RESULTS

We found that EWSAT1 was highly expressed in CRC tissues and cell lines and associated with poor overall survival. In vitro, knockdown of EWSAT1 suppressed the cell proliferation, migration and invasion. Moreover, miR-326 was found to be a target of EWSAT1, and miR-326 inhibitor could partially reverse the effects on CRC cell progression induced by si-EWSAT1. Subsequently, we validated FBXL20 as a vital downstream target for miR-326, and EWSAT1 positively regulated FBXL20 via miR-326 in vitro. In addition, these findings were confirmed by in vivo experiments.

CONCLUSION

Taken together, the data showed that EWSAT1 promoted CRC progression via targeting miR-326/FBXL20 pathway, which might provide a novel therapeutic target for CRC treatment.

MIWI prevents aneuploidy during meiosis by cleaving excess satellite RNA

MIWI, a murine member of PIWI proteins mostly expressed during male meiosis, is crucial for piRNA biogenesis, post-transcriptional regulation, and spermiogenesis. However, its meiotic function remains unknown. Here, we report that MIWI deficiency alters meiotic kinetochore assembly, significantly increases chromosome misalignment at the meiosis metaphase I plate, and causes chromosome mis-segregation. Consequently, Miwi-deficient mice show elevated aneuploidy in metaphase II and spermatid death. Furthermore, in Miwi-null and Miwi slicer-deficient mutants, major and minor satellite RNAs from centromeric and pericentromeric satellite repeats accumulate in excess. Over-expression of satellite repeats in wild-type spermatocytes also causes elevated chromosome misalignment, whereas reduction of both strands of major or minor satellite RNAs results in lower frequencies of chromosome misalignment. We show that MIWI, guided by piRNA, cleaves major satellite RNAs, generating RNA fragments that may form substrates for subsequent Dicer cleavage. Furthermore, Dicer cleaves all satellite RNAs in conjunction with MIWI. These findings reveal a novel mechanism in which MIWI- and Dicer-mediated cleavage of the satellite RNAs prevents the over-expression of satellite RNAs, thus ensuring proper kinetochore assembly and faithful chromosome segregation during meiosis.

LncRNA SNHG7 Functions as an Oncogene in Cervical Cancer by Sponging miR-485-5p to Modulate JUND Expression

BACKGROUND

Long non-coding RNA (LncRNA) SNHG7 is involved in the development of multiple cancers. However, its role in cervical cancer (CC) has not been elucidated. This study aimed to explore the function of SNHG7 in CC progression and the underlying mechanisms.

MATERIALS AND METHODS

The expression levels of SNHG7 and miR-485-5p in CC tissues and cell lines were measured by qPCR. Functional experiments including CCK-8 assay, wound healing assay, transwell assay, flow cytometry, Western blot, luciferases reporter assay and immunoprecipitation (RIP) were performed to explore the SNHG7/miR-485-5p/JUND pathway. Additionally, in vivo study was carried out by establishing tumor xenograft models.

RESULTS

We found that SNHG7 was markedly enhanced in CC tissues and cell lines, and associated with poor clinical characteristics. In vitro, knockdown of SNHG7 inhibited CC cell proliferation, migration and invasion, as well as aggravated cell apoptosis. As to mechanism investigation, rescue experiments revealed that miR-485-5p inhibitor could partially reverse the effects on CC cells induced by SNHG7 knockdown. SNHG7 upregulated JUND expression via miR-485-5p. Moreover, tumor xenograft models were established to confirm the findings in vivo.

CONCLUSION

SNHG7 promoted CC progression through miR-485-5p/JUND axis. The SNHG7/miR-485-5p/JUND pathway might provide a novel therapeutic target for CC treatment.

Centromeric Non-Coding RNAs: Conservation and Diversity in Function

Chromosome segregation is strictly regulated for the proper distribution of genetic material to daughter cells. During this process, mitotic chromosomes are pulled to both poles by bundles of microtubules attached to kinetochores that are assembled on the chromosomes. Centromeres are specific regions where kinetochores assemble. Although these regions were previously considered to be silent, some experimental studies have demonstrated that transcription occurs in these regions to generate non-coding RNAs (ncRNAs). These centromeric ncRNAs (cenRNAs) are involved in centromere functions. Here, we describe the currently available information on the functions of cenRNAs in several species.

Saccharomyces cerevisiae Centromere RNA Is Negatively Regulated by Cbf1 and Its Unscheduled Synthesis Impacts CenH3 Binding

Two common features of centromeres are their transcription into noncoding centromere RNAs (cen-RNAs) and their assembly into nucleosomes that contain a centromere-specific histone H3 (cenH3). Here, we show that Saccharomyces cerevisiae cen-RNA was present in low amounts in wild-type (WT) cells, and that its appearance was tightly cell cycle-regulated, appearing and disappearing in a narrow window in S phase after centromere replication. In cells lacking Cbf1, a centromere-binding protein, cen-RNA was 5-12 times more abundant throughout the cell cycle. In WT cells, cen-RNA appearance occurred at the same time as loss of Cbf1's centromere binding, arguing that the physical presence of Cbf1 inhibits cen-RNA production. Binding of the Pif1 DNA helicase, which happens in mid-late S phase, occurred at about the same time as Cbf1 loss from the centromere, suggesting that Pif1 may facilitate this loss by its known ability to displace proteins from DNA. Cen-RNAs were more abundant in rnh1Δ cells but only in mid-late S phase. However, fork pausing at centromeres was not elevated in rnh1Δ cells but rather was due to centromere-binding proteins, including Cbf1 Strains with increased cen-RNA lost centromere plasmids at elevated rates. In cbf1Δ cells, where both the levels and the cell cycle-regulated appearance of cen-RNA were disrupted, the timing and levels of cenH3 centromere binding were perturbed. Thus, cen-RNAs are highly regulated, and disruption of this regulation correlates with changes in centromere structure and function.

LncRNA SNHG7 promotes pancreatic cancer proliferation through ID4 by sponging miR-342-3p

BACKGROUND

Small nucleolar RNA host gene 7 (SNHG7) is a novel identified oncogenic gene in tumorigenesis. However, the role that SNHG7 plays in pancreatic cancer (PC) remains unclear. In this study, we aimed to investigate the functional effects of SNHG7 on PC and the possible mechanism.

METHODS

The expression levels of SNHG7 in tissues and cell lines were measured by RT-qPCR. Cell viability, apoptosis, migration and invasion were examined to explore the function of SNHG7 on PC. Bioinformatics methods were used to predict the target genes. The mechanism was further investigated by transfection with specific si-RNA, miRNA mimics or miRNA inhibitor. Tumor xenograft was carried out to verify the effects of SNHG7 in vivo.

RESULTS

We found that SNHG7 was overexpressed in both PC tissues and cell lines. High expression level of SNHG7 was correlated with the poor prognosis. SNHG7 knockdown inhibited the proliferation, migration and invasion of PC cells. Moreover, SNHG7 was found to regulate the expression of ID4 via sponging miR-342-3p. Additionally, this finding was supported by in vivo experiments.

CONCLUSIONS

LncRNA SNHG7 was overexpressed in PC tissues, and knockdown of SNHG7 suppressed PC cell proliferation, migration and invasion via miR-342-3p/ID4 axis. The results indicated that SNHG7 as a potential target for clinical treatment of PC.

Long non-coding RNA GAS5 suppresses pancreatic cancer metastasis through modulating miR-32-5p/PTEN axis

Background

Long non-coding RNA growth arrest-specific transcript 5 (lncRNA GAS5) is a well-known tumor suppressor in the pathogenesis of a variety of human cancers. The precise role of GAS5 in pancreatic cancer (PC) progression is currently unknown, so the aim of this study was to explore the functional participation of GAS5 in PC metastasis.

Methods

The expression changes of GAS5, miR-32-5p and PTEN in human PC specimens and cell lines were compared by means of molecular biology methods. Transfection of the recombinant plasmid was applied to modulate the expression levels of the target genes. RIP and RNA pull-down assays were designed to investigate the interaction between GAS5 and miR-32-5p. The effect of GAS5 and miR-32-5p on PC progression was assessed with cell proliferation, migration, invasion and apoptosis in vitro.

Results

GAS5 and PTEN protein were decreased in human PC tissues and cells, but miR-32-5p was increased. GAS5 induction greatly inhibited the proliferation, migration and invasion of PC cells PANC-1 and BxPC-3 in vitro and simultaneously induced cell apoptosis. Moreover, GAS5 positively regulated the expression of PTEN through miR-32-5p. Furthermore, GAS5 suppressed the proliferation, migration and invasion of PC cells through regulating miR-32-5p/PTEN axis. Additionally, this finding was further supported by the results of in vivo experiments.

Conclusion

GAS5 could positively regulate PTEN-induced tumor-suppressor pathway via miR-32-5p, thereby suppressing PC metastasis.

Electronic supplementary material

The online version of this article (10.1186/s13578-017-0192-0) contains supplementary material, which is available to authorized users.