Histone H2a mRNA interacts with Lin28 and contains a Lin28-dependent posttranscriptional regulatory element

Lin28 has been shown to block the processing of let-7 microRNAs implicated in the regulation of cell growth and differentiation. Here, we show that Lin28 also specifically associates with ribonucleoprotein particles containing the replication-dependent histone H2a mRNA in mouse embryonic stem cells. We further show that the coding region of H2a mRNA harbors high affinity binding sequences for Lin28 and that these sequences stimulate the expression of reporter genes in a Lin28-dependent manner. We suggest that a key function of Lin28 in the maintenance of pluripotency is to promote the expression of the H2a gene (and perhaps also other replication-dependent histone genes) at the posttranscriptional level in order to coordinate histone production with the unique proliferative properties of embryonic stem cells

The H19/let-7 double-negative feedback loop contributes to glucose metabolism in muscle cells

The H19 lncRNA has been implicated in development and growth control and is associated with human genetic disorders and cancer. Acting as a molecular sponge, H19 inhibits microRNA (miRNA) let-7. Here we report that H19 is significantly decreased in muscle of human subjects with type-2 diabetes and insulin resistant rodents. This decrease leads to increased bioavailability of let-7, causing diminished expression of let-7 targets, which is recapitulated in vitro where H19 depletion results in impaired insulin signaling and decreased glucose uptake. Furthermore, acute hyperinsulinemia downregulates H19, a phenomenon that occurs through PI3K/AKT-dependent phosphorylation of the miRNA processing factor KSRP, which promotes biogenesis of let-7 and its mediated H19 destabilization. Our results reveal a previously undescribed double-negative feedback loop between sponge lncRNA and target miRNA that contributes to glucose regulation in muscle cell

Lin28 Regulates BMP4 and Functions with Oct4 to Affect Ovarian Tumor Microenvironment

Emerging evidence suggests that the tumor microenvironment plays a critical role in regulating cancer stem cells (CSCs) and tumor progression through both autocrine and paracrine signaling. Elevated production of bone morphogenetic proteins (BMPs) from human ovarian cancer cells and stroma has been shown to increase CSC proliferation and tumor growth. Here, we report that Lin28, a stem cell factor, binds to BMP4 mRNA in epithelial ovarian carcinoma cells thereby promoting BMP4 expression at the posttranscriptional level. As co-expression of Lin28 and Oct4 (another stem cell factor) has been implicated in ovarian cancer CSCs, we also determined that high levels of Lin28 are associated with an unfavorable prognosis when co-expressed with high levels of Oct4. Together, these findings uncover a new level of regulation of BMP4 expression, and imply a novel Lin28/Oct4/BMP4-mediated mechanism of regulating ovarian tumor cell growth, thus holding potential for the development of new strategies for the diagnosis and treatment of ovarian cancer.This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Landes Bioscience and can be found at: http://www.landesbioscience.com/journals/cc/.Keywords: Ovarian cancer, Posttranscriptional, BMP4, Tumor microenvironment, Lin28/Oct

Determinants of mRNA recognition and translation regulation by Lin28

Lin28 is critical for stem cell maintenance and is also associated with advanced human malignancies. Our recent genome-wide studies mark Lin28 as a master post-transcriptional regulator of a subset of messenger RNAs important for cell growth and metabolism. However, the molecular basis underpinning the selective mRNA target regulation is unclear. Here, we provide evidence that Lin28 recognizes a unique motif in multiple target mRNAs, characterized by a small but critical ‘A’ bulge flanked by two G:C base pairs embedded in a complex secondary structure. This motif mediates Lin28-dependent stimulation of translation. As Lin28 is also known to inhibit the biogenesis of a cohort of miRNAs including let-7, we propose that Lin28 binding to different RNA types (precursor miRNAs versus mRNAs) may facilitate recruitment of different co-factors, leading to distinct regulatory outcomes. Our findings uncover a putative yet unexpected motif that may constitute a mechanistic base for the multitude of functions regulated by Lin28 in both stem cells and cancer cells

Nucleocytoplasmic transport of mRNA

The movement of mRNA from the nucleus to the cytoplasm is one of the crucial checkpoints in the regulation of gene expression. However, the molecular mechanism of RNA transport is largely unknown. The aim of this thesis is to investigate some of the rules that govern this process.^ The first part of the thesis is focused on how the process of splicing affects mRNA export. The specific questions asked were whether the process of splicing promotes the export of mRNA from the nucleus, or whether removal of splice sites is actually required. The mouse polyoma virus was used as a model system to approach these issues. Results led to the proposal that the process of splicing in the polyoma system is not necessary for mRNA export, nor does it make export more efficient. Instead, removal of splicing machinery from mRNA may be required for export.^ The second part of the thesis was to learn how naturally intronless gene transcripts are transported from the nucleus to the cytoplasm and to determine whether these transcripts contain positive cis-acting transport elements. By using a variety of approaches, a novel cis-acting transport element, called HTE, contained within the mouse histone H2a gene coding region was identified. This element facilitates the cytoplasmic accumulation of intronless gene transcripts and of unspliced HIV-1-related mRNAs. HTE is the first example of cellular element that has such functions.^ The last part of the thesis was to determine the role of polyadenylation in mRNA nuclear export. By exploiting a cis-acting ribozyme that uncouples 3\sp\prime end formation from the cellular polyadenylation machinery, evidence that polyadenylation is a prerequisite for mRNA nuclear export and that a long stretch of poly(A) near the 3\sp\prime end of an mRNA is not sufficient for mRNA export was obtained.

Emerging roles of long noncoding RNAs in neurological diseases and metabolic disorders

Long noncoding RNAs (lncRNAs) are a new class of transcripts that are in general longer than 200 nucleotides and that have no protein-coding potential. The vast majority of vertebrate genomes encode diverse and complex lncRNAs that play regulatory roles at almost every step of gene expression. Recently, increasing evidence has implicated lncRNAs in the pathogenesis of various human diseases. The purpose of the Research Topic, "Emerging roles of long noncoding RNAs in neurological diseases and metabolic disorders", is to bring together leading researchers in the field who, through contributing to an organized and comprehensive collection of peer-reviewed articles, provide a broad perspective on the latest advances in the field. A number of interesting and cutting-edge areas will be covered as below, but this list is not exclusive: - The methodologies and technologies of identifying and studying lncRNAs - LncRNAs in gene-specific transcription - LncRNAs in epigenetic regulation - LncRNAs in post-transcriptional regulation - LncRNAs in disease - Mapping of noncoding single nucleotide polymorphisms associated with disease