Long RNA-Mediated Chromatin Regulation in Fission Yeast and Mammals

ASAR lncRNAs control DNA replication timing through interactions with multiple hnRNP/RNA binding proteins

ASARs are a family of very-long noncoding RNAs that control replication timing on individual human autosomes, and are essential for chromosome stability. The eight known ASAR lncRNAs remain closely associated with their parent chromosomes. Analysis of RNA-protein interaction data (from ENCODE) revealed numerous RBPs with significant interactions with multiple ASAR lncRNAs, with several hnRNPs as abundant interactors. An ~7 kb domain within the ASAR6-141 lncRNA shows a striking density of RBP interaction sites. Genetic deletion and ectopic integration assays indicate that this ~7 kb RNA binding protein domain contains functional sequences for controlling replication timing of entire chromosomes in cis. shRNA-mediated depletion of 10 different RNA binding proteins, including HNRNPA1, HNRNPC, HNRNPL, HNRNPM, HNRNPU, or HNRNPUL1, results in dissociation of ASAR lncRNAs from their chromosome territories, and disrupts the synchronous replication that occurs on all autosome pairs, recapitulating the effect of individual ASAR knockouts on a genome-wide scale. Our results further demonstrate the role that ASARs play during the temporal order of genome-wide replication, and we propose that ASARs function as essential RNA scaffolds for the assembly of hnRNP complexes that help maintain the structural integrity of each mammalian chromosome.

Thirty Years with ERH: An mRNA Splicing and Mitosis Factor Only or Rather a Novel Genome Integrity Protector?

ERH is a 100 to about 110 aa nuclear protein with unique primary and three-dimensional structures that are very conserved from simple eukaryotes to humans, albeit some species have lost its gene, with most higher fungi being a noteworthy example. Initially, studies on Drosophila melanogaster implied its function in pyrimidine metabolism. Subsequently, research on Xenopus laevis suggested that it acts as a transcriptional repressor. Finally, studies in humans pointed to a role in pre-mRNA splicing and in mitosis but further research, also in Caenorhabditis elegans and Schizosaccharomyces pombe, demonstrated its much broader activity, namely involvement in the biogenesis of mRNA, and miRNA, piRNA and some other ncRNAs, and in repressive heterochromatin formation. ERH interacts with numerous, mostly taxon-specific proteins, like Mmi1 and Mei2 in S. pombe, PID-3/PICS-1, TOST-1 and PID-1 in C. elegans, and DGCR8, CIZ1, PDIP46/SKAR and SAFB1/2 in humans. There are, however, some common themes in this wide range of processes and partners, such as: (a) ERH homodimerizes to form a scaffold for several complexes involved in the metabolism of nucleic acids, (b) all these RNAs are RNA polymerase II transcripts, (c) pre-mRNAs, whose splicing depends on ERH, are enriched in transcripts of DNA damage response and DNA metabolism genes, and (d) heterochromatin is formed to silence unwanted transcription, e.g., from repetitive elements. Thus, it seems that ERH has been adopted for various pathways that serve to maintain genome integrity.

Long non-coding RNA TRIM52-AS1 sponges microRNA-577 to facilitate diffuse large B cell lymphoma progression via increasing TRIM52 expression

Diffuse large B cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma (NHL) globally, featuring heterogeneous clinical phenotypes and altered molecular manifestations. The long non-coding ribose nucleic acids (lncRNAs) play crucial roles in the diagnosis, treatment, and prognosis of DLBCL, requiring the exploration of complex functions and mechanisms. In this study, the expression of lncRNA TRIM52-AS1 in DLBCL tissues from the Cancer Genome Atlas (TCGA) database was initially analyzed and correlated to the data from collected clinical samples. Then, the significance of TRIM52-AS1 on the diagnosis and prognosis of DLBCL patients was predicted with the receiver-operating characteristic (ROC) curve and Kaplan-Meier (KM) analysis. Further, cell counting kit (CCK)-8, EdU staining, and flow cytometry analyses were performed to assess the effect of TRIM52-AS1 on DLBCL cell proliferation, apoptosis, and cell cycle. Then, the mechanism of TRIM52-AS1 sponging miR-577 to increase TRIM52 expression was explored using a starBase prediction approach, dual-luciferase reporter, RNA immunoprecipitation assay (RIPA), quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and Western blot analyses. The experimental results confirmed the overexpression of TRIM52-AS1 in the DLBCL cell lines. Further, the high expression of TRIM52-AS1 predicted the poor Ann Arbor stage and were correlated with the presence of B symptoms, high international prognostic index, and poor disease prognosis. TRIM52-AS1 knockdown inhibited the DLBCL cell proliferation, and induced apoptosis and G0/G1 cycle arrest. Interestingly, the overexpression of TRIM52-AS1 increased the mRNA stability of TRIM52 through binding IGFBP3 protein and upregulated the TRIM52 protein expression by sponging miR-577. Together, the overexpressed TRIM52-AS1 could promote the DLBCL progression through IGFBP3/miR-218-5p/TRIM52 axis, highlighting the clinical significance of TRIM52-AS1 in the DLBCL diagnosis.