Fig 2: KTN1 inhibits the interaction between PRMT1 and TRIM48. (A) HEK293FT cells with or without KTN1 down-regulation were transfected with a Flag-PRMT1 plasmid and the indicated mutated HA-UB plasmids or wild-type HA-UB plasmid. Then, ubiquitinated PRMT1 proteins were pulled down with an anti-HA antibody and immunoblotted with an anti-Flag antibody. (B) TRIM48 expression was knocked down in control or KTN1-depleted cells, and the expression of PRMT1 was then examined by Western blot assay. (C) The expression of PRMT1 was examined after TRIM48 was overexpressed in control or KTN1-overexpressing cells. (D) HGC-27 and MKN-45 cells expressing Flag-PRMT1 and His-TRIM48 proteins were transiently transfected with or without MYC-KTN1, and then a proximity ligation assay was performed with anti-Flag and anti-His antibodies. Scale bar = 5 µm. (E) The histogram demonstrates the quantification of PLA-identified signaling, which is shown in Figure 7D. (F) After transfecting the Flag-PRMT1 plasmid and different doses of the MYC-KTN1 plasmid into HEK293FT cells, the Flag-PRMT1 protein was pulled down using an anti-Flag antibody and immunoblotted with the indicated antibodies to determine the degree of interaction between PRMT1 and TRIM48. *P < 0.05, **P < 0.01, ***P < 0.001.

Fig 3: Schematic diagram showing PRMT1-enhanced gastric cancer metastasis mediated by the ß-catenin signaling pathway in vitro and in vivo. In the cytoplasm, KTN1 inhibits K48-linked polyubiquitination of PRMT1 by decreasing the interaction between TRIM48 and PRMT1. Then, in the nucleus, PRMT1 recruits MLXIP to the ß-catenin promoter and transcriptionally activates the ß-catenin signaling pathway. PRMT1 promotes gastric cancer cell proliferation, migration, and invasion of in vitro and tumor growth and metastasis in vivo.