Regulatory miPEP Open Reading Frames Contained in the Primary Transcripts of microRNAs

This review aims to consider retrospectively the available data on the coding properties of pri-microRNAs and the regulatory functions of their open reading frames (ORFs) and the encoded peptides (miPEPs). Studies identifying miPEPs and analyzing the fine molecular mechanisms of their functional activities are reviewed together with a brief description of the methods to identify pri-miRNA ORFs and the encoded protein products. Generally, miPEPs have been identified in many plant species of several families and in a few animal species. Importantly, molecular mechanisms of the miPEP action are often quite different between flowering plants and metazoan species. Requirement for the additional studies in these directions is highlighted by alternative findings concerning negative or positive regulation of pri-miRNA/miRNA expression by miPEPs in plants and animals. Additionally, the question of how miPEPs are distributed in non-flowering plant taxa is very important for understanding the evolutionary origin of such micropeptides. Evidently, further extensive studies are needed to explore the functions of miPEPs and the corresponding ORFs and to understand the full set of their roles in eukaryotic organisms. Thus, we address the most recent integrative views of different genomic, physiological, and molecular aspects concerning the expression of miPEPs and their possible fine functions

Regulatory miPEP Open Reading Frames Contained in the Primary Transcripts of microRNAs

This review aims to consider retrospectively the available data on the coding properties of pri-microRNAs and the regulatory functions of their open reading frames (ORFs) and the encoded peptides (miPEPs). Studies identifying miPEPs and analyzing the fine molecular mechanisms of their functional activities are reviewed together with a brief description of the methods to identify pri-miRNA ORFs and the encoded protein products. Generally, miPEPs have been identified in many plant species of several families and in a few animal species. Importantly, molecular mechanisms of the miPEP action are often quite different between flowering plants and metazoan species. Requirement for the additional studies in these directions is highlighted by alternative findings concerning negative or positive regulation of pri-miRNA/miRNA expression by miPEPs in plants and animals. Additionally, the question of how miPEPs are distributed in non-flowering plant taxa is very important for understanding the evolutionary origin of such micropeptides. Evidently, further extensive studies are needed to explore the functions of miPEPs and the corresponding ORFs and to understand the full set of their roles in eukaryotic organisms. Thus, we address the most recent integrative views of different genomic, physiological, and molecular aspects concerning the expression of miPEPs and their possible fine functions

Insulin receptor-related receptor in the pancreas and in a β-cell line

Insulin receptor-related receptor (IRR) belongs to the family of the insulin receptor (IR) along with the IR itself and the insulin-like growth factor receptor. Whereas the ligands of the latter receptors are known, identification of an IRR ligand has eluded investigations so that IRR has been considered an orphan receptor. A recent breakthrough in the understanding of IRR functional role came from the finding that IRR can be activated by mildly alkali media in absence of any protein agonist [1]. IRR shows highly specific tissue distribution, with highest concentration in kidney intercalated cells. However, significant amounts of the receptor are also found in the stomach and in α- and β-cells of the islets of Langerhans. Recent reports indicate that the pancreatic duct system is frequently associated with islet cells. Here, we show that those islet cells that are in contact with the excretory ducts are also IRR-expressing cells. Thus, when the exocrine pancreas is in an active state of secretion duct-associated islet cell behavior is potentially influenced by an IRR-mediated alkaline-induced signalling pathway. To explore this issue, we analyzed the effects of alkaline media on the pancreatic β-cell line MIN6. Activation of endogenous IRR was detected and could be inhibited with linsitinib, a synthetic inhibitor of the IR family of receptors. IRR autophosphorylation correlated with pH-dependent linsitinib-sensitive activation of IR substrate 1 (IRS-1). In contrast to insulin stimulation, no protein kinase B (Akt/PKB) phosphorylation was detected as a result of the alkali treatment. The alkaline medium but not insulin also triggered actin cytoskeleton remodeling in MIN6 cells that was blocked by pre-incubation with linsitinib. We propose that the activation of IRR by alkali is a component of a local loop of signaling between the exocrine and endocrine parts of the pancreas

TAS3 miR390-dependent loci in non-vascular land plants: towards a comprehensive reconstruction of the gene evolutionary history

Trans-acting small interfering RNAs (ta-siRNAs) are transcribed from protein non-coding genomic TAS loci and belong to a plant-specific class of endogenous small RNAs. These siRNAs have been found to regulate gene expression in most taxa including seed plants, gymnosperms, ferns and mosses. In this study, bioinformatic and experimental PCR-based approaches were used as tools to analyze TAS3 and TAS6 loci in transcriptomes and genomic DNAs from representatives of evolutionary distant non-vascular plant taxa such as Bryophyta, Marchantiophyta and Anthocerotophyta. We revealed previously undiscovered TAS3 loci in plant classes Sphagnopsida and Anthocerotopsida, as well as TAS6 loci in Bryophyta classes Tetraphidiopsida, Polytrichopsida, Andreaeopsida and Takakiopsida. These data further unveil the evolutionary pathway of the miR390-dependent TAS3 loci in land plants. We also identified charophyte alga sequences coding for SUPPRESSOR OF GENE SILENCING 3 (SGS3), which is required for generation of ta-siRNAs in plants, and hypothesized that the appearance of TAS3-related sequences could take place at a very early step in evolutionary transition from charophyte algae to an earliest common ancestor of land plants