An XIST-related small RNA regulates KRAS G-quadruplex formation beyond X-inactivation

LncRNAs: the good, the bad, and the unknown

Long non-coding RNAs (lncRNAs) are significant contributors in maintaining genomic integrity through epigenetic regulation. LncRNAs can interact with chromatin-modifying complexes in both cis and trans pathways, drawing them to specific genomic loci and influencing gene expression via DNA methylation, histone modifications, and chromatin remodeling. They can also operate as building blocks to assemble different chromatin-modifying components, facilitating their interactions and gene regulatory functions. Deregulation of these molecules has been associated with various human diseases, including cancer, cardiovascular disease, and neurological disorders. Thus, lncRNAs are implicated as potential diagnostic indicators and therapeutic targets. This review discusses the current understanding of how lncRNAs mediate epigenetic control, genomic integrity, and their putative functions in disease pathogenesis.

Interaction between non-coding RNAs, mRNAs and G-quadruplexes

G-quadruplexes are secondary helical configurations established between guanine-rich nucleic acids. The structure is seen in the promoter regions of numerous genes under certain situations. Predicted G-quadruplex-forming sequences are distributed across the genome in a non-random way. These structures are formed in telomeric regions of the human genome and oncogenic promoter G-rich regions. Identification of mechanisms of regulation of stability of G-quadruplexes has practical significance for understanding the molecular basis of genetic diseases such as cancer. A number of non-coding RNAs such as H19, XIST, FLJ39051 (GSEC), BC200 (BCYRN1), TERRA, pre-miRNA-1229, pre-miRNA-149 and miR-1587 have been found to contain G-quadraplex-forming regions or affect configuration of these structures in target genes. In the current review, we outline the recent research on the interaction between G-quadruplexes and non-coding RNAs, other RNA transcripts and DNA molecules.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection: Triggering a Lethal Fight to Keep Control of the Ten-Eleven Translocase (TET)-Associated DNA Demethylation?

The extended and diverse interference of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in multiple host functions and the diverse associated symptoms implicate its involvement in fundamental cellular regulatory processes. The activity of ten-eleven translocase 2 (TET2) responsible for selective DNA demethylation, has been recently identified as a regulator of endogenous virus inactivation and viral invasion, possibly by proteasomal deregulation of the TET2/TET3 activities. In a recent report, we presented a detailed list of factors that can be affected by TET activity, including recognition of zinc finger protein binding sites and bimodal promoters, by enhancing the flexibility of adjacent sequences. In this review, we summarize the TET-associated processes and factors that could account for SARS-CoV-2 diverse symptoms. Moreover, we provide a correlation for the observed virus-induced symptoms that have been previously associated with TET activities by in vitro and in vitro studies. These include early hypoxia, neuronal regulation, smell and taste development, liver, intestinal, and cardiomyocyte differentiation. Finally, we propose that the high mortality of SARS-CoV-2 among adult patients, the different clinical symptoms of adults compared to children, the higher risk of patients with metabolic deregulation, and the low mortality rates among women can all be accounted for by the complex balance of the three enzymes with TET activity, which is developmentally regulated. This activity is age-dependent, related to telomere homeostasis and integrity, and associated with X chromosome inactivation via (de)regulation of the responsible XIST gene expression.

The long noncoding RNA LUCAT1 promotes colorectal cancer cell proliferation by antagonizing Nucleolin to regulate MYC expression

The long noncoding RNA (lncRNA) LUCAT1 was recently reported to be upregulated and to play an essential role in multiple cancer types, especially colorectal cancer (CRC), but the molecular mechanisms of LUCAT1 in CRC are mostly unreported. Here, a systematic analysis of LUACT1 expression is performed with data from TCGA database and clinic CRC samples. LUCAT1 is identified as a putative oncogene, which is significantly upregulated in CRC and is associated with poor prognosis. Loss of LUCAT1 restricts CRC proliferative capacities in vitro and in vivo. Mechanically, NCL is identified as the protein binding partner of LUCAT1 by using chromatin isolation by RNA purification coupled with mass spectrometry (ChIRP-MS) and RNA immunoprecipitation assays. We also show that NCL directly binds to LUCAT1 via its putative G-quadruplex-forming regions from nucleotides 717 to 746. The interaction between LUCAT1 and NCL interferes NCL-mediated inhibition of MYC and promote the expression of MYC. Cells lacking LUCAT1 show a decreased MYC expression, and NCL knockdown rescue LUCAT1 depletion-induced inhibition of CRC cell proliferation and MYC expression. Our results suggest that LUCAT1 plays a critical role in CRC cell proliferation by inhibiting the function of NCL via its G-quadruplex structure and may serve as a new prognostic biomarker and effective therapeutic target for CRC.