| Gastric cancer is the fifth commonest cancer and the fourth leading cause of cancer mortality worldwide.China accounted for approximately 44%of the total number of gastric cancer worldwide.In the same time,gastric cancer is the second most frequently diagnosed cancer and the second leading cause of cancer-related death in China.The cause of gastric cancer is related to many factors,such as unhealthy dietary habits,living environment,HP infection and so on.Surgical resection combined with chemotherapy is the first choice for the treatment of gastric cancer.The first-line drug regimen in most cases is the combination of fluoropyrimidine,oxaliplatin and trastuzumab.At present,the analysis of biomarkers related to gastric cancer is still not comprehensive enough.With the update of human genome annotation,it is found that long non-coding RNAs(lncRNA)exist in huge amounts and perform critical bio-functions in both normal tissues and disease development,especially in cancer disease.Using a combination of genomics,proteomics,and computational approaches,extensive lncRNA transcripts were discovered to bind with ribosomes and translated into peptides.Those novel peptides may locate in cytoplasm,nucleus,mitochondria or endoplasmic reticulum in accordance with their special biological functions.We utilized the RegRNA 2.0,CPC2,and CPAT algorithms to calculate translation scores of the ORF(Opening reading frames)hidden within the transcripts of lncRNAs.Ribosome-profiling data helped us find out the RNA sequence protected by ribosomes.LncRNA Disease and NONCODE databases were used to find the expression relevance of lncRNAs between tumor and normal tissues.Through the integrated usage of those databases,38 novel potential lncRNAs were subsequently identified.By the construction of ORF plasmids,cellular immunofluorescence,MS analysis and antibody production,we proved that LncRNA GHET1 transcript harbors an ORF sequence and subsequently translates into a unique mitochondrial peptide,named as GOMP(GHET1-ORF encoded mitochondrial peptide).GOMP was proved to directly interact with ATP synthase,ATP5A1,in the inner-membrane of mitochondria.GOMP was found to be a nutrient stress-induced micropeptide that responded to glucose deprivation.Through GOMP stably overexpressing cancer cells construction and RNA-sequence analysis,genes related with mitochondrial biogenesis and mitochondrial translational factors were discovered to be significantly up-regulated compared with control cells in mRNA level.By the detection of oxygen consumption rate,ATP amounts,cellular lactate and glucose in culture medium,it was proved that GOMP could shift gastric cancer metabolic patterns to mitochondrial oxidative phosphorylation.We next investigated the post-translational modifications of GOMP.Cancer cells were treated with inhibitors of autophagy and ubiquitin-proteasome system respectively,results showed that GOMP was degraded by 26s proteasome in cytoplasm.CO-IP assay followed by MS analysis identified two proteins,E3 ligase TRIM25 and ribosome binding protein UBA52,participating in regulating protein levels of GOMP.The interference of siRNAs was carried out to discover that TRIM25 promoted GOMP degradation via ubiquitin modification,and UBA52 increased GOMP micropeptide expression levels.Additionally,TRIM25 played a vital role in upregulating GOMP levels under energy stress.Last but not least,we investigated the influence of GOMP in gastric cancer tumorgenesis.Overexpression of GOMP promoted cancer cell proliferation and migration both in vitro and in vivo assay.Additionally,overexpression of GOMP maintained cell survival ability under glucose starvation through synthesizing ATP.This research firstly identified a bio-functional micropeptide GOMP,and provided a new research idea for clinical treatment of gastric cancer from the prospective of tumor metabolic reprogramming. |
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