UXT, a novel DNMT3b-binding protein, promotes breast cancer progression via negatively modulating lncRNA MEG3/p53 axis.

Overexpressed ubiquitously expressed transcript (UXT) in breast tumors and derived cell lines modulated the transcriptional activity of estrogen receptor alpha. However, how UXT exerts its biological functions in the tumorigenicity of breast cancer remains largely unknown. Expressions of UXT and maternally expressed gene 3 (MEG3) were examined by qRT-PCR and Western blot. The capacity of cell proliferation, apoptosis, migration, and invasion was assessed using CCK-8, flow cytometry, and transwell assays. Methylation-specific PCR (MS-PCR) was employed to evaluate the methylation of the MEG3 imprinting control region. Co-immunoprecipitation was performed to verify the UXT/DNMT3b interaction. RNA immunoprecipitation (RIP) was subjected to assess the regulation of MEG3 on p53 activity. A xenograft tumor model was further conducted to certify the molecular mechanism. UXT was upregulated, while MEG3 was downregulated in breast cancer tissues and cell lines. UXT knockdown or MEG3 overexpression inhibited cell proliferation, promoted apoptosis, and weakened cell migration and invasion. Hypermethylation of the MEG3 imprinting control region was modulated by highly expressed DNMT3b. UXT inhibited MEG3 expression via recruiting DNMT3b to its imprinting control region. MEG3 positively regulated p53 activity. UXT negatively regulated the MEG3/p53 axis in a DNMT3b-dependent manner to promote tumor growth. UXT, a novel DNMT3b-binding protein, aggravates the progression of breast cancer through MEG3/p53 axis.