| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 98 === Myb-binding protein 1a (Mybbp1a) is a nuclear protein, and was first identified by its ability to interact with c-Myb. Mybbp1a was reported to interact with other transcription factors. However, the exact role of Mybbp1a in the transcription regulation is still unclear. To address this issue, we performed gene expression microarray analysis to search for potential Mybbp1a downstream target genes. We subsequently found that H19 mRNA expression was significantly increased in siMybbp1a C2C12 cell line. H19 is conserved in mammals and encodes a long noncoding RNA that is under the regulation of genomic imprinting, and seems to play a role in some cancers. Our real-time RT-PCR experiments confirmed that Mybbp1a negatively regulates H19 expression. Furthermore, based on DNA methylation profiling and ChIP analyses, we demonstrated that such Mybbp1a-mediated regulation was mediated neither through Igf2-H19 imprinting control region (ICR) DNA methylation nor ICR occupancy of the insulator protein CTCF. Instead, transcription activity of a H19 promoter-reporter construct was highly increased in Mybbp1a knockdown cells, suggesting the Mybbp1a directly modulates the H19 promoter. Interestingly, while the methylation of H19 promoter did not seem to change in siMybbp1a cells, we discovered that promoter-associated histone H3K9 acetylation underwent significant up-regulation upon Mybbp1a knockdown. Finally, the molecular mechanism of Mybbp1a-regulated H19 expression is discussed.
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