Introduction
It is of great significance to expand understanding of the development mechanism and improve the therapeutic effect of gastric cancer. The protein arginine methyl transferase 1 (PRMT1) catalyzing the asymmetric dimethylation of histone H4 on arginine 3 (H4R3me2a) and activating gene transcription, has been demonstrated to promote cancer development in various tumors. However, the expression and mechanism of PRMT1 in gastric cancer are still poorly understood.
Aims & Methods
Immunohistochemistry was performed on gastric cancer tissue chip to evaluate the expression situation of PRMT1 and its relationship with the prognosis of related patients. shPRMT1 lentivirus, SFN overexpression plasmids or deletion mutant PRMT1(PRMT1Δ, mutating the S-adenosylmethionine binding site) overexpression plasmids were used to interfere the expression of corresponding genes, and CCK8, EDU and transwell experiments were employed to evaluate the functional changes of gastric cancer cells on proliferation, metastasis and invasion. Pull down proteins of H4R3me2a antibody were detected by mass spectrometry, and validated with COIP experiments. Immunofluorescence (IF) and/or nucleocytoplasmic separation experiments were used to evaluate the cellular localization of H4R3me2a and SFN. RNA-seq was performed to detect the mRNA expression differences affected by knocking down PRMT1 or SFN. Western blot and qPCR were employed to verify gene expression changes on protein and mRNA levels.
Results
PRMT1 is significantly overexpressed in gastric cancer compared to adjacent tissues, and its high expression is closely related to poor prognosis. Knocking down PRMT1 could significantly inhibit the proliferation, migration, and invasion of gastric cancer cells, while overexpression of PRMT1Δ had similar effects. These results indicate that PRMT1 promotes the progression of gastric cancer in a methyltransferase activity dependent manner. The results of mass spectrometry of H4R3me2a antibody pull-down protein and further CoIP confirmed the binding relationship of SFN and H4R3me2a. The results of IF showed that SFN and H4R3me2a colocalized in the nucleus of gastric cancer cells, while the nuclear distribution of SFN was also found by the nucleoplasmic separation experiments. In terms of function, overexpression of SFN significantly enhanced the proliferation, migration, and invasion of gastric cancer cells, while simultaneous knocking down PRMT1 or overexpressing PRMT1Δ could reverse these effects. RNA-seq results showed that FOXQ1 was one of the common downstream target genes of PRMT1 and SFN, which was further proved by western bolt and qPCR. More significantly, PRMT1 inhibitor AMI-1could reverse the increase of FOXQ1 mRNA expression caused by SFN overexpression. These above results indicate that SFN is a main associated protein of H4R3me2a, and cooperates with PRMT1 to promote the progression of gastric cancer.
Conclusion
PRMT1 mediated H4R3me2a recruits SFN to co-regulate downstream target genes expression and promote gastric cancer progression.
