The flightless I protein interacts with RNA-binding proteins and is involved in the genome-wide mRNA post-transcriptional regulation in lung carcinoma cells.

The flightless I protein (FLII) belongs to the gelsolin family. Its function has been associated with actin remodeling, embryonic development, wound repair, and more recently with cancer. The structure of FLII is characterized by the N-terminal leucine-rich repeats (LRR) and C-terminal gesolin related repeated units that are both protein-protein inter-action domains, suggesting that FLII may exert its function by interaction with other proteins. Therefore, systematic study of protein interactions of FLII in cells is important for the understanding of FLII functions. In this study, we found that FLII was downregulated in lung carcinoma cell lines H1299 and A549 as compared with normal HBE (human bronchial epithelial) cell line. The investigation of FLII interactome in H1299 cells revealed that 74 of the total 132 putative FLII interactors are involved in RNA post-transcriptional modification and trafficking. Furthermore, by using high-throughput transcriptome and translatome sequencing combined with cell fractionation, we showed that the overexpression or knockdown of FLII impacts on the overall nuclear export, and translation of mRNAs. IPA analysis revealed that the majority of these target mRNAs encode the proteins whose functions are reminiscent of those previously reported for FLII, suggesting that the post-transcriptional regulation of mRNA might be a major mechanism of action for FLII.