Identification of hypoxia-induced isoforms and novel genes with nanopore long reads sequencing

Long-read nanopore sequencing is capable of continuously reading thousands of base pairs. Here, we report the application of nanopore sequencing technology for analysing hypoxia-specific transcriptomes in normal liver and liver cancer cell lines, which help us to better understand the mechanism of cell survival and metastasis under hypoxia. We conducted transcriptomic sequencing of normal liver and liver cancer cell lines under normoxia or hypoxia, founding that long-read sequencing could detect thousands of hypoxia-specific isoforms and unannotated novel genes. At the cellular level, we have verified that the novel gene 644 is most up-regulated novel gene under hypoxic conditions. We observed that the novel gene 644 possesses classical mRNA characteristics, with its CDS region encoding 91 amino acids. Through protein structure predictions, we discovered that the novel gene 644 contains a transmembrane domain. Experimental validation confirmed that the novel gene 644 is a membrane protein, and knockdown of the novel gene 644 significantly suppresses the proliferative capacity of liver cancer cells under hypoxic conditions. Furthermore, we revealed the protein structure alteration of hypoxia specific isoforms with molecular dynamics simulation. The results indicate that our hypoxic dataset can serve as a foundation for the structural simulation of hypoxic-specific proteins. In summary, we have presented a hypoxic-specific third-generation sequencing dataset for further analysis, which provides sufficient details on cellular transcriptomes and is particularly valuable for understanding the survival and metastasis of tumor under hypoxic conditions. From this dataset, we have validated the importance of novel gene 644 for tumor survival under hypoxia and identified alterations in hypoxic-specific protein structures. These discoveries can bring us new knowledge about hypoxia, leading to the identification of potential tumor treatment targets and biomarkers. Overall design: To figure out the influence of hypoxia on liver cancer cell with nanopore sequencing, we treated THLE-3 and Hep3B cell lines in 48 hours under normoxia or hypoxia and extracted mRNA for furthur nanopore sequencing.