Brm transactivates the telomerase reverse transcriptase (TERT) gene and modulates the splicing patterns of its transcripts in concert with p54nrb
Brm transactivates the telomerase reverse transcriptase (TERT) gene and modulates the splicing patterns of its transcripts in concert with p54nrb
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DOI：
10.1042/bj20071075
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发表时间：
2008-04-01
影响因子：
4.1
通讯作者：
Iba, Hideo
中科院分区：
文献类型：
--
作者：
Ito, Taiji;Watanabe, Hirotaka;Iba, Hideo
我们报道了DBHS（果蝇行为，人类剪接）家族蛋白p54（nrb）结合BRG1 （Brahma相关基因1）和Brm (Brahma), SWI/SNF（开关/糖不可发酵）染色质重塑复合物的催化亚基，以及该复合物的另一个核心亚基BAF60a。p54（nrb）的n端区域足以拉下SWI/SNF复合物的其他核心亚基，这表明p54（nrb）可以结合SWI/SNF样复合物。PSF （polypyy嘧啶束结合蛋白相关剪接因子）是已知直接结合p54（nrb）的DBHS家族蛋白，也被发现与SWI/ snf样复合体相关。当靶向Brm的sh（短发夹）rna在brg1缺陷的人细胞系（NCI-H1299）中逆转录时，所得到的克隆显示端粒酶逆转录酶（TERT）基因下调，外显子7和8被排除的TERT mRNA的比例增加，TERT mRNA编码β位点缺失的无活性蛋白。所有这些克隆在brm敲除后2个月内都表现出生长停滞。在NCI-H1299细胞中，Brm、p54（nrb）、PSF和RNA聚合酶II在CTD （c端结构域）Ser(2)上磷酸化，特异性地共定位在TERT外显子7的一个包含备选剪接受体位点的区域。这些发现表明，在人类肿瘤细胞中含有功能性SWI/SNF复合物的TERT基因位点，Brm，可能还有BRG1，与p54（nrb）协同，将启动有效的转录，并可能通过加速外显子包合参与TERT转录本的后续剪接，这在一定程度上有助于端粒酶活性的维持。
We report that a DBHS (Drosophila behaviour, human splicing) family protein, p54(nrb), binds both BRG1 (Brahma-related gene 1) and Brm (Brahma), catalytic subunits of the SWI/SNF (switch/sucrose non-fermentable) chromatin remodelling complex, and also another core subunit of this complex, BAF60a. The N-terminal region of p54(nrb) is sufficient to pull-down other core subunits of the SWI/SNF complex, suggesting that p54(nrb) binds SWI/SNF-like complexes. PSF (polypyrimidine tract-binding protein-associated splicing factor), another DBHS family protein known to directly bind p54(nrb), was also found to associate with the SWI/SNF-like complex. When sh (short hairpin) RNAs targeting Brm were retrovirally expressed in a BRG1-deficient human cell line (NCI-H1299), the resulting clones showed down-regulation of the TERT (telomerase reverse transcriptase) gene and an enhancement of ratios of exon-7-and-8-excluded TERT mRNA that encodes a beta-site-deleted inactive protein. All of these clones display growth arrest within 2 months of the Brm-knockdown. In NCI-H1299 cells, Brm, p54(nrb), PSF and RNA polymerase II phosphorylated on CTD (C-terminal domain) Ser(2) specifically co-localize at a region incorporating an alternative splicing acceptor site of TERT exon 7. These findings suggest that, at the TERT gene locus in human tumour cells containing a functional SWI/SNF complex, Brm, and possibly BRG1, in concert with p54(nrb), would initiate efficient transcription and could be involved in the subsequent splicing of TERT transcripts by accelerating exon-inclusion, which partly contributes to the maintenance of active telomerase.