UBTF mediates activation of L3MBTL2 to suppress NISCH expression through histone H2AK119 monoubiquitination modification in breast cancer.

Lethal(3)malignant brain tumor-like protein 2 (L3MBTL2) has been related to transcriptional inhibition and chromatin compaction. Nevertheless, the biological functions and mechanisms of L3MBTL2 are undefined in breast cancer (BRCA). Here, we revealed that L3MBTL2 is responsible for the decline of Nischarin (NISCH), a well-known tumor suppressor, in BRCA, and explored the detailed mechanism. Knockdown of L3MBTL2 reduced monoubiquitination of histone H2A at lysine-119 (H2AK119ub), leading to reduced binding to the NISCH promoter and increased expression of NISCH. Meanwhile, the knockdown of L3MBTL2 decreased proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of BRCA cells, and increased apoptosis, which were abated by NISCH knockdown. Nucleolar transcription factor 1 (UBTF) induced the transcription of L3MBTL2 in BRCA, and the suppressing effects of UBTF silencing on EMT in BRCA cells were also reversed by NISCH knockdown. Knockdown of UBTF slowed tumor progression and attenuated lung tumor infiltration, whereas simultaneous knockdown of NISCH accelerated EMT and increased tumor lung metastasis. Taken together, our results show that L3MBTL2, transcriptionally activated by UBTF, exerts oncogenic functions in BRCA, by catalyzing H2AK119Ub and reducing expression of NISCH.