Inhibiting XPOT suppresses TNBC growth via downregulating specific tRNA- TTC19 pathway mediating cytokinesis failure

Background: Transfer RNAs (tRNAs) are transported to the cytoplasm participating in mRNA translation through carrying cognate aminoacyl amino acids to ribosomes. Accumulating evidence shows that tRNAs play an important role in development and progression of various cancers, including breast cancer. However, it is still poorly clarified whether and how individual tRNA is modulated in triple negative breast cancer (TNBC) progression. Methods Clinical value of XPOT was explored in breast cancer cohorts. TNBC cell lines with XPOT silence were used for in vitro and in vivo experiments. RNA-seq, tRNA high throughput sequencing and Protein mass spectrometry of XPOT were performed for exploring the underlying molecular mechanism of XPOT promoting TNBC growth. Results XPOT (Exportin-T), a nuclear export protein receptor of tRNAs, was associated with poor prognosis of breast cancer. In vitro experiments showed XPOT knockdown could inhibit TNBC cells proliferation. RNA-seq results indicated that XPOT was involved in the cytokinesis completion of TNBC cells. High throughput sequencing of tRNA revealed that XPOT specifically influenced a subset of tRNA isodecoders nucleo-cytoplasmic trafficking including tRNA-Ala-AGC-10-1. Mechanistically, we found that XPOT preferentially transported nuclear tRNA-Ala-AGC-10-1 to the cytoplasm and drove the translation of TPR Repeat Protein 19 (TTC19) through codon preferential analysis and protein mass spectrometry analysis. TTC19 was also indispensable for cytokinesis and proliferation of TNBC cells. Conclusions Together, these findings provide a novel regulatory translation mechanism of preferential tRNA isodecoder nucleo-cytoplasmic transport through XPOT to modulate biological behavior of TNBC. This regulation mode could coordinate the spatial location of specific tRNA and the translation of mRNA, to facilitate TNBC proliferation and progression. Targeting XPOT may serve as a novel potential therapeutic strategy for TNBC.