The Role And Mechanism Of Histone Lysine Methylation Binding Protein L3MBTL3 In Promoting Breast Cancer Cells Migration And Invasion

Breast cancer is the most common malignant tumor in women.Globally,breast cancer is the cancer with the highest number of new cases.Breast cancer metastases are a challenge in the treatment of breast cancer and a major cause of death in breast cancer patients.L3MBTL3 is an important member of the methyl lysine readers MBT family.Proteins containing MBT domains play important roles in differentiation,development and disease.Analysis of the breast cancer dataset(GSE12276)by the Breast Cancer Integrative Platform revealed a negative correlation between L3MBTL3 and survival without distant metastasis in breast cancer patients,suggesting that L3MBTL3 might promote breast cancer metastasis,but the specific mechanism remains to be studied.Therefore,we will explore the role and mechanism of L3MBTL3 in breast cancer migration and invasion.In breast cancer cells,our study found that L3MBTL3 promoted cell migration and invasion.By comparing RNA-seq and ChIP-seq results of L3MBTL3,we found that SNAIL was a downstream target gene of L3MBTL3.SNAIL is an important EMT transcription factor,which can promote EMT and tumor cells metastasis.Our study demonstrated that L3MBTL3 binding to the SNAIL promoter region(-563.474)promoted SNAIL transcription and induced EMT.The results of mass spectrometry indicated that L3MBTL3 interacted with STAT3.STAT3 is often activated in breast cancer,and activated STAT3 promotes breast cancer metastasis by regulating the expression of downstream target genes.Our study demonstrated that L3MBTL3 interacted with p-STAT3(Y705).Further studies revealed that L3MBTL3 recruited p-STAT3(Y705)to the SNAIL promoter region(-563,-474)and promoted SNAIL transcription.Inhibition of STAT3 expression inhibited the role of L3MBTL3 in promoting SNAIL transcription as well as the role of L3MBTL3 in promoting breast cancer cell migration and invasion.Taken together,our study revealed a novel mechanism that L3MBTL3 recruited p-STAT3(Y705)to the SNAIL promoter region(-563.-474)and promoted SNAIL transcription,thereby inducing EMT and promoting breast cancer cells migration and invasion.To provide a theoretical basis for the treatment of breast cancer metastasis.SUMOylation modifications have multiple effects on the biological functions of proteins.We identified L3MBTL3 as a potential SUMOylated protein by online SUMOplotTM software.Our study demonstrated that L3MBTL3 was a SUMOylation protein in breast cancer cells,and its main SUMOylation sites were K88 and K679.The mutation of K679 site could reduce the protein stability of L3MBTL3.Furthermore,we demonstrated that L3MBTL3 interacted with SNAIL,and found that SUMOylation of L3MBTL3 enhanced its interaction with SNAIL and LSD1.The mutation of SUMOylation sites of L3MBTL3 inhibited breast cancer cells migration.Taken together,we revealed that SUMOylation of L3MBTL3 could enhance its interaction with SNAIL and LSD1,as well as promoting breast cancer cells migration.This new mechanism will help provide a rationale for precision treatment of breast cancer metastasis.