Structural MitoLab, Structural Biology Department, Maria de Maeztu Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), 08028 Barcelona, Spain.
Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, 08028 Barcelona, Spain.
Nucleic Acids Res. 2019 Jul 9;47(12):6519-6537. doi: 10.1093/nar/gkz406.
Human mitochondrial DNA (h-mtDNA) codes for 13 subunits of the oxidative phosphorylation pathway, the essential route that produces ATP. H-mtDNA transcription and replication depends on the transcription factor TFAM, which also maintains and compacts this genome. It is well-established that TFAM activates the mtDNA promoters LSP and HSP1 at the mtDNA control region where DNA regulatory elements cluster. Previous studies identified still uncharacterized, additional binding sites at the control region downstream from and slightly similar to LSP, namely sequences X and Y (Site-X and Site-Y) (Fisher et al., Cell 50, pp 247-258, 1987). Here, we explore TFAM binding at these two sites and compare them to LSP by multiple experimental and in silico methods. Our results show that TFAM binding is strongly modulated by the sequence-dependent properties of Site-X, Site-Y and LSP. The high binding versatility of Site-Y or the considerable stiffness of Site-X tune TFAM interactions. In addition, we show that increase in TFAM/DNA complex concentration induces multimerization, which at a very high concentration triggers disruption of preformed complexes. Therefore, our results suggest that mtDNA sequences induce non-uniform TFAM binding and, consequently, direct an uneven distribution of TFAM aggregation sites during the essential process of mtDNA compaction.
人线粒体 DNA(h-mtDNA)编码氧化磷酸化途径的 13 个亚基,这是产生 ATP 的必要途径。h-mtDNA 的转录和复制依赖于转录因子 TFAM,它还维持和压缩这个基因组。众所周知,TFAM 在 mtDNA 控制区激活 mtDNA 启动子 LSP 和 HSP1,而 DNA 调节元件在该区域聚集。先前的研究在 LSP 的下游和稍相似的位置(即序列 X 和 Y(Site-X 和 Site-Y))确定了尚未被表征的其他结合位点(Fisher 等人,Cell 50,第 247-258 页,1987 年)。在这里,我们通过多种实验和计算方法探索 TFAM 在这两个位点的结合,并将其与 LSP 进行比较。我们的结果表明,TFAM 结合受 Site-X、Site-Y 和 LSP 的序列依赖性特性强烈调节。Site-Y 的高结合多功能性或 Site-X 的相当大的刚性调节 TFAM 相互作用。此外,我们表明 TFAM/DNA 复合物浓度的增加诱导多聚化,而在非常高的浓度下,会触发预形成复合物的破坏。因此,我们的结果表明 mtDNA 序列诱导非均匀的 TFAM 结合,并因此在 mtDNA 压缩的基本过程中直接导致 TFAM 聚集位点的不均匀分布。