在12月19日出版的Science雜志上,，麻省理工及Koch研究所,，生物學(xué)系， 白頭研究所生物醫(yī)學(xué)研究中心,，薩克研究Crick-Jacobs中心的科學(xué)家研究發(fā)現(xiàn)基因組序列上的啟動(dòng)子區(qū)域存在多樣的分支轉(zhuǎn)錄現(xiàn)象,。
對(duì)大部分的基因來說與RNA聚合酶II相連的轉(zhuǎn)錄起始位點(diǎn)都被認(rèn)為是單向性的。在本研究中,，麻省理工等處的研究小組找出充足的證據(jù)證實(shí)編碼蛋白的基因啟動(dòng)子區(qū)存在有分支轉(zhuǎn)錄的現(xiàn)象,。轉(zhuǎn)錄起始位點(diǎn)與RNAs相連的區(qū)域（Transcription start site-associatied RNAs,TSSa-RNAs）非隨機(jī)地從側(cè)面激活啟動(dòng)子，在活性高峰期,，反義與正義短RNAs各自位于TSSs（轉(zhuǎn)錄起始位點(diǎn)）的上游250個(gè)核苷酸的位置和TSSs下游50個(gè)核苷酸的位置,。用Northern雜交技術(shù)分析顯示，TSSa-RNAs是一類長度在20-90nt大小的RNA子群,。啟動(dòng)子相關(guān)的RNA聚合酶II與H3K4-trimethylated histone以及轉(zhuǎn)錄起始標(biāo)志（Transcription initiation hallmarks）都共同定位于正義和反義TSSs-RNA區(qū),；然而，H3K4-trimethylated histone延伸的特殊RNA聚合酶II只存在于TSSs的下游,。
這些研究結(jié)果表明,，啟動(dòng)子活性區(qū)域短距離內(nèi)存在分支轉(zhuǎn)錄現(xiàn)象，這一現(xiàn)象可能有助于啟動(dòng)子區(qū)域維持平衡,，確保次級(jí)調(diào)節(jié)活性,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science 19 December 2008:DOI: 10.1126/science.1162253
Divergent Transcription from Active Promoters
Amy C. Seila,1* J. Mauro Calabrese,1,2* Stuart S. Levine,3 Gene W. Yeo,4 Peter B. Rahl,3 Ryan A. Flynn,1 Richard A. Young,2,3 Phillip A. Sharp1,2
Transcription initiation by RNA polymerase II (RNAPII) is thought to occur unidirectionally from most genes. Here, we present evidence of widespread divergent transcription at protein-encoding gene promoters. Transcription start site–associated RNAs (TSSa-RNAs) nonrandomly flank active promoters, with peaks of antisense and sense short RNAs at 250 nucleotides upstream and 50 nucleotides downstream of TSSs, respectively. Northern analysis shows that TSSa-RNAs are subsets of an RNA population 20 to 90 nucleotides in length. Promoter-associated RNAPII and H3K4-trimethylated histones, transcription initiation hallmarks, colocalize at sense and antisense TSSa-RNA positions; however, H3K79-dimethylated histones, characteristic of elongating RNAPII, are only present downstream of TSSs. These results suggest that divergent transcription over short distances is common for active promoters and may help promoter regions maintain a state poised for subsequent regulation.
1 Koch Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2 Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3 Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA.
4 Salk Institute, Crick-Jacobs Center for Theoretical and Computational Biology, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
