Human MYCT1 cDNA was first cloned using in silicon hybridization and molecular methods and previously
AbstractYY1 is a key transcription factor and plays different roles in various cancers. However, role and mechanism of YY1 in laryngeal cancer are still unknown. YY1 and MYCT1 mRNA and protein levels were detected by Real-time RT-PCR and Western Blot methods, respectively. Binding of YY1 to MYCT1 promoter was predicted and confirmed by bioinformatics and chromatin immunoprecipitation assays, respectively. MYCT1 promoter activity was assessed by dual luciferase assay system. Laryngeal cancer cell proliferation, migration, and apoptosis were evaluated by cell viability, colony formation, cell scratch assay, transwell assay, and flow cytometry methods, respectively. YY1 and MYCT1 were upregulated and downregulated at transcriptional level in laryngeal cancer, respectively, which showed a negative correlation between YY1 and MYCT1 expression in laryngeal cancer. Significantly higher expression of YY1 and lower expression of MYCT1 were found in laryngeal cancer tissues of patients with lymphatic metastasis than those without metastasis.YY1 directly bound to MYCT1 promoter region and inhibited its promoter activity. YY1 silence had similar biological functions as MYCT1 overexpression in repressiveness of proliferation and migration, and promotion of apoptosis in laryngeal cancer cells. However, the effects of YY1 silence were recovered by MYCT1 knockdown. YY1 promotes proliferation and migration with suppression of apoptosis via directly inhibiting MYCT1 in laryngeal cancer cells, suggesting that YY1 is a useful target as a potential oncogene in laryngeal cancer development and progression. implying that MYCT1 function in cancer is tissue-specific. For example, MYCT1 is downregulated and promotes apoptosis in laryngeal and gastric cancer [1,2]. However, MYCT1 is upregulated and enhances cancer cell viability in acute myeloid leukemia [3]. Therefore, study on MYCT1 regulation network helps us to understand the tissuespecific manner of MYCT1 in cancer.At present, several transcription factors have been reported to be a direct regulator of MYCT1. In our and other studies, C-MYC directly targets MYCT1 promoter region and regulates its expression [1,[4][5][6]. We also found that MYCT1 promoter region including C-MYC binding site is hypermethylated in laryngeal cancer, suggesting that the methylation status interferes with the binding of C-MYC to MYCT1 leading to MYCT1 dysregulation in laryngeal cancer [7]. Liddiard et al. discovered that the fusion protein RUNX-ETO contributes to key aspects of the leukemic phenotypes via targeting MYCT1 [3]. In addition to C-MYC and RUNX-ETO, other transcription factors regulating MYCT1 expression are not reported.YY1 (Yin-Yang-1) is a zinc-finger transcription factor that belongs to the GLI-Krüppel gene family [8] and abnormally expressed in lots of cancer such as colon cancer [9], non-small-cell lung cancer [10], and myeloma [11], indicating that it has key roles in carcinogenesis. Ho...