| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 97 === Nucleophosmin (NPM, B23) is a multifunctional protein that plays crucial role in ribosome biogenesis, cell cycle progression, apoptosis and cell differentiation regulation. In recent years, B23 has been found to interact with many transcription factors to regulate gene transcription. However, the exact role of B23 in the transcription regulation is still unclear. Here, we undertook an integrated functional genomic approach, which combines microarray and ChIP-on-chip analyses, to globally identify putative B23-target genes. Real-time PCR and chromatin precipitation (ChIP) assay were used to further confirm the putative B23-target genes. Through such integration approach, we have so far identified several candidate genes of B23-controlled transcription and chosen one of the candidates - histone genes for further characterization. ChIP assay revealed B23 occupancy of several histone gene promoters and that two markers of histone gene activation, NPAT and histone H4 acetylation, were upregulated in the absence of B23. During S phase, siRNA-mediated knockdown of B23 prolonged the expression of histone genes, transcription of which is normally restricted to early S phase. Therefore B23 may act as a repressor for histone genes and also a regulator of S phase progression. Our findings further indicated that B23 may participate in negatively regulating histone genes expression during cell growth arrest and differentiation. In the future we will focus on elucidating the molecular mechanism underlying B23-mediated regulation of histone genes and investigating its biological relevance.
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