Genome-wide transcriptome and translatome analyses reveal the role of protein extension and domestication in liver cancer oncogenesis.

One gene could be transcribed to different RNA isoforms, and then produce various forms of protein sequences. This mechanism largely diversifies the cellular pool and allows natural selection to select from a wider range of substrates. In the cancer field, the isoform switches between tumor and normal tissues, such as the alternative splicing, stop codon read-through, or protein domestication, are significantly ignored by the traditional differential expression analyses. The intention of this work is to fill this gap. We collected public transcriptome and translatome data from ten patients with liver cancer, and performed genome-wide comparison on the stop codon read-through and protein domestication events. Both events diversify the proteome during long-term evolution. Surprisingly, we found that the tumor tissues globally have higher occurrence of stop codon read-through events as well as protein domestication events (translation signals of non-coding repetitive elements). These read-through and domestication events show limited overlapping across the ten patients, indicating the randomness of their occurrence and their deleterious nature. These tumor-specific events might have been purged by natural selection if they are not collected timely. Our work manifests the role of protein extension and domestication in liver cancer oncogenesis, adding new aspects to the cancer field.