A ZTF-7/RPS-2 Complex Mediates The Cold-warm Response In C. Elegans

Temperature is a very common stimulus for all organisms.The fluctuation of environmental temperature affects life activities such as protein homeostasis,regulation of gene expression and development.Physiological responses to sustain temperature changes constitute a critical adaptive mechanism for living organisms.Many studies are focused on heat shock response,but how organisms respond to cold shock stimuli is largely unclear.The RNA exosome complex is a ribonuclease complex composed of 10 or 11 subunits and is conserved in eukaryotes such as yeast,Arabidopsis,zebrafish,mouse and human.One critical function of the RNA exosome is to produce mature,properly processed rRNAs for the ribosome.Other RNA targets include small ncRNAs that are processed,including snRNA,snoRNA,tRNA and so on.Finally,the RNA exosome contributes to quality control by degrading aberrant,improperly processed RNA transcripts.The RNA exosome complex plays an important role in maintaining RNA metabolic homeostasis and normal growth and development of organism.RNA exosome complex has two main localization modes in Caenorhabditis elegans(C.elegans):Exo10DIS-3 complex,which consists of DIS-3 as the catalytic subunit,is mainly localized in the nucleoplasm,and Exo10EXOS-10 complex,which is composed of EXOS-10 as the catalytic active subunit,is localized in the nucleoplasm and nucleolus,and is enriched in the nucleolus.Here,we observed that the The Exo10EXOS-10 complex responds to the hypothermic stress by altering its subcellular localization in C.elegans.The Exo10EXOS-10 complex is localized in nucleoli when the worms were grown at 20℃.Growth at 40C for 3 hours per se did not alter the nucleolar localization of Exo10EXOS-10 complex.However,after recovery at 20℃ for 0.5 hour,Exol0EXOS-10 complex exhibited dramatic depletion from the nucleoli but enrichment in the nucleoplasm.When recovered at 20℃ for 5 hours,Exo10EXOS-10 complex regained nucleolar localization in the nucleoli.The subcellular localization of Exo10DIS-3 complex was not altered after cold stimulation.Meanwhile,the low temperature induced Exo10EXOS-10 complex localization change is not affected by the known low-temperature regulatory pathways,such as glutamate receptor-3(glr3)and asp-17/zip-10 genetic pathways.Taken together,the data suggest that a novel mechanism by which C.elegans responds to environmental cold-warm exposure.To understand the mechanism of the cold-warm response,we conducted forward genetic screening and identified ZTF-7,which is required for Exo10EXOS-10 complex depletion from nucleoli upon transient cold-warm exposure in C.elegans.ZTF-7 is an evolutionarily conserved protein with clusters of C2H2-type zinc finger domains and is predicted to be an ortholog of human ZNF277.Some studies have reported that ZNF277 is associated with the occurrence of various cancers and neurological diseases in humans.ZNF277 is highly expressed in colon cancer and ovarian cancer tissues,ZNF277 microdeletions may contribute to the risk of language impairments.A coldwarm treatment at 4℃ for 3 hours followed by recovery at 20℃ could not deplete the Exo10EXOS-10 complex from the nucleoli to nucleoplasm in ztf-7 mutants.The ztf-7 mutants have a brood size similar to that of wild-type N2 animals at 20℃ but have a much lower number of progeny at 25℃.We assayed the lifespan of ztf-7 mutants.The ztf-7 mutation did not pronouncedly affect the lifespan of animals at both 20℃ and 25℃.To further understand how ZTF-7 regulates cold-warm shock-induced Exo10EXOS10 complex translocation,we identified that ZTF-7 interacts with a small ribosomal subunit protein RPS-2 through immunoprecipitation followed by mass spectrometry(IP-MS).Knocking down rps-2 significantly blocked cold-warm shock-induced Exo10EXOS-10 complex translocation.RPS-2 is one of the proteins of the small ribosome subunits and participates in pre-rRNA processing and nuclear export of pre-40S subunits in fission yeast.Notably,the depletion of rps-2 by RNAi resulted in a significant reduction of the mRNA levels of ztf-7.Additionally,other small ribosomal subunit proteins,for example RPS-0 and RPS-12,were also involved in the cold-warm shock-induced Exo10EXOS-10 complex translocation.Therefore,this study found that the Exo10EXOS-10 complex specifically responds to the low-temperature stimulation in C.elegans to maintain the homeostasis of rRNA in the nucleus,and reveals the regulatory mechanism of Exol0EXOS-10 complex localization changes.Our research has a great significance for understanding the response of organisms when they confront with the stimulation of cold environment.