Architectural role of mitochondrial transcription factor A in maintenance of human mitochondrial DNA
Architectural role of mitochondrial transcription factor A in maintenance of human mitochondrial DNA
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DOI：
10.1128/mcb.24.22.9823-9834.2004
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发表时间：
2004-11-01
影响因子：
5.3
通讯作者：
Kang, DC
中科院分区：
文献类型：
--
作者：
Kanki, T;Ohgaki, K;Kang, DC
线粒体转录因子A（mitochondrialtranscription factor A，TFAM）是线粒体DNA（mitochondrialDNA，mtDNA）的转录因子，具有非特异性结合DNA的特性，对mtDNA的维持至关重要。为了阐明TFAM的作用，我们通过RNA干扰抑制HeLa细胞中内源性TFAM的表达。TFAM的含量在干扰后第3天下降到正常水平的15%左右，然后逐渐恢复。线粒体DNA的数量变化与TFAM的日变化密切相关，而在细胞器中，线粒体DNA的转录在第3天维持在正常水平的50%左右。缺乏其C-末端25个氨基酸的TFAM（TFAM-DeltaC）在体外略微激活转录。当TFAM-DeltaC在HeLa细胞中以与内源性TFAM相当的水平表达时，mtDNA增加两倍，表明TFAM-DeltaC在这些条件下与内源性TFAM一样能够维持mtDNA。表达TFAM-DeltaC的细胞的细胞器内转录并不比对照中的多。因此，mtDNA的量与TFAM的量密切相关，但与转录水平无关。我们讨论了TFAM在维护线粒体DNA的建筑作用，除了其在转录激活中的作用。
Mitochondrial transcription factor A (TFAM), a transcription factor for mitochondrial DNA (mtDNA) that also possesses the property of nonspecific DNA binding, is essential for maintenance of mtDNA. To clarify the role of TFAM, we repressed the expression of endogenous TFAM in HeLa cells by RNA interference. The amount of TFAM decreased maximally to about 15% of the normal level at day 3 after RNA interference and then recovered gradually. The amount of mtDNA changed closely in parallel with the daily change in TFAM while in organello transcription of mtDNA at day 3 was maintained at about 50% of the normal level. TFAM lacking its C-terminal 25 amino acids (TFAM-DeltaC) marginally activated transcription in vitro. When TFAM-DeltaC was expressed at levels comparable to those of endogenous TFAM in HeLa cells, mtDNA increased twofold, suggesting that TFAM-DeltaC is as competent in maintaining mtDNA as endogenous TFAM under these conditions. The in organello transcription of TFAM-DeltaC-expressing cells was no more than that in the control. Thus, the mtDNA amount is finely correlated with the amount of TFAM but not with the transcription level. We discuss an architectural role for TFAM in the maintenance of mtDNA in addition to its role in transcription activation.