A chromatin landmark and transcription initiation at most promoters in human cells (Cell, 2007, 130:77-88)

報告日期: 2008/05/13
報告時間: 17:10/18:00
報告學生: 林世杰
講評老師: 孫孝芳


A Chromatin Landmark and Transcription Initiation at Most Promoters in Human Cells

Cell 130, 77–88, July 13, 2007

Speaker: Shih-Chieh Lin(林世杰)

Commentator: Hsiao-Fang Sunny Sun (孫孝芳) 老師


Place: Room 602




In the nuclei of all eukaryotic cells, genomic DNA is highly folded by histone and nonhistone proteins, and formed a dynamic structure called chromatin. Chromatin modifications including histone modifications are associated with transcriptional status. Acetylation of histone H3 lysine 9 and 14, and methylation of histone H3 lysine 4, 36 and 79 are marks for active transcription. Transcriptional regulation can occur at many levels, but the major steps are transcriptional initiation and elongation. These regulatory steps are also associated with specific histone modification. For example: tri-methylation of H3 lysine 4 (H3K4me3) and acetylation of H3 lysine 9, 14 (H3K9,13Ac) are located in the promoter regions and associated with transcriptional initiation, and trimethylation of H3 lysine 36 (H3K36me3) is occurred in the transcribed portions of active protein-coding genes and associated with elongation. However, the relationship between transcriptional activity and chromatin state in human embryonic stem (ES) cells is still a puzzle and need to be further investigated. Therefore, the author used ChIP on chip method to screen the expression profiles of several histone marks across whole genome and correlate with microarray expression data in human ES cells. According to these data, they found that protein-coding genes fall into three groups of regulatory behavior. The actively transcribed genes are contained histone modifications that are marks of both initiation and elongation, and these generally produce detectable transcripts. A second group contained transcriptional initiation without evidence of transcripts elongation or accumulation. The third group consisted of clustered genes that didn’t contain the mark of transcriptional initiation. In summary, the author found that transcription initiation and histone H3K4me3 modification occur at the promoters of most protein-coding genes in human cells. This may create a more accessible chromatin structure and serve a landmark for regulatory molecules.



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