Characterization Of CircRNAs In Two Holophilic Archaea And Tetrahymena Thermophila

Circular RNA(circRNA)is a special type of RNA,which forms covalent-closed continuous loop in most cases through 5' to 3'ends via back-splicing in animals.CircRNAs demonstrate certain degree of conservation and show some tissue specificity in multicellular animals.A large number of circRNAs have been identified in many species,in which some of them have important biological functions.Archaea,as one of the three major areas of phylogenetic trees,are closer to eukaryotes at the molecular level.Therefore,It is an essential part of evolution and classification of species.Tetrahymena thermophila is a well-suited model system to study chromatin biology and investigate gene expression regulatory layers.Tetrahymena features two distinct nuclei,a macronucleus(MAC)and a micronucleus(MIC),present within the same cell.In this paper,two halophilic archaea-Haloferax mediterranei,Haloarcula hispanica and Tetrahymena thermophila is selected.The composition of circRNA,the location on the chromosome of circRNA was analyzed in depth through RNA-seq technology and bioinformatics analyses.Verification of certain sequenced circRNAs were also conducted.We detected 67 circRNAs in Haloferax mediterranei and 133 circRNAs in Haloarcula hispanica.CircRNA is mainly located on two archaea chromosomes,specifically on 16S rRNA,23S rRNA,16S rRNA-23S rRNA,and protein-coding genes.We detected 109 circRNAs in Tetrahymena B2086.circRNA is mainly found in protein-coding genes.There are three types of circRNAs in Tetrahymena B2086:exonic,intronic,and intergenic.Among them,exonic accounts for the largest proportion.Most of the exon circRNAs involved in loop formation are less than four.We have also discovered that the host genes of the Tetrahymena circRNA mainly play ATP-binding,protein-binding,nucleic acid-binding,and protein kinase functions in molecular functions.In biological processes,they mainly participate in multiple biological processes such as translation,protein phosphorylation,ion transport,ATP synthesis,metabolism.This study is of significance to better understand the molecular properties and other related issues of archaea and Tetrahymena circRNA,and hopefully shed a novel light on the evolution of life and the origin of eukaryotes.