Architectural Role of Mitochondrial Transcription Factor A in Maintenance of Human Mitochondrial DNA

Kanki, Tomotake; Ohgaki, Kippei; Gaspari, Martina; Gustafsson, Claes M.; Fukuoh, Atsushi; Sasaki, Narie; Hamasaki, Naotaka; Kang, Dongchon

doi:10.1128/mcb.24.22.9823-9834.2004

Cited by 275 publications

(242 citation statements)

References 43 publications

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“…This finding led to the conclusion that mitochondrial transcription is a two-component system also in higher cells, much similar to the situation in yeast. However, this model is not easy to reconcile with findings from other laboratories that have demonstrated that TFAM is an essential mammalian transcription factor both in vivo and in vitro (6,15,22). We here investigate the role of TFAM for transcription initiation in a defined in vitro system.…”

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confidence: 64%

Mammalian transcription factor A is a core component of the mitochondrial transcription machinery

Shi

Dierckx

Wanrooij

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Transcription factor A (TFAM) functions as a DNA packaging factor in mammalian mitochondria. TFAM also binds sequence-specifically to sites immediately upstream of mitochondrial promoters, but there are conflicting data regarding its role as a core component of the mitochondrial transcription machinery. We here demonstrate that TFAM is required for transcription in mitochondrial extracts as well as in a reconstituted in vitro transcription system. The absolute requirement of TFAM can be relaxed by conditions that allow DNA breathing, i.e., low salt concentrations or negatively supercoiled DNA templates. The situation is thus very similar to that described in nuclear RNA polymerase II-dependent transcription, in which the free energy of supercoiling can circumvent the need for a subset of basal transcription factors at specific promoters. In agreement with these observations, we demonstrate that TFAM has the capacity to induce negative supercoils in DNA, and, using the recently developed nucleobase analog FRET-pair tC O -tC nitro , we find that TFAM distorts significantly the DNA structure. Our findings differ from recent observations reporting that TFAM is not a core component of the mitochondrial transcription machinery. Instead, our findings support a model in which TFAM is absolutely required to recruit the transcription machinery during initiation of transcription.T he mtDNA is a double-stranded circular molecule that encodes 22 tRNAs, 2 rRNAs, and 13 subunits of the respiratory chain. Transcription is initiated from two sites, the light-and heavy-strand promoters (LSP and HSP1, respectively), and proceeds to produce near genome-length polycistronic transcripts, which are subsequently processed to generate the individual RNA molecules (1). Transcription from LSP also produces the RNA primers required for initiation of mtDNA replication at the origin of the heavy strand (2-4). In vivo experiments have identified a second transcription initiation site (HSP2) downstream of HSP1, but the sequence requirements of this promoter remain to be defined (5, 6).In budding yeast, the basic machinery for mtDNA transcription consists only of two factors: the mitochondrial RNA polymerase (Rpo41) and its accessory factor Mtf1, also denoted sc-mtTFB (1). In mammalian cells, it has been reported that mitochondrial transcription also requires the transcription factor A (TFAM), a high-mobility group-box (HMG) protein (7,8). TFAM plays a role as an mtDNA packaging factor that can bind, wrap, and bend DNA in a non-sequence-specific manner (9-12). TFAM also binds sequence-specifically to sites upstream (−15 to −35) of the HSP1 and LSP transcription start sites (13,14). The human mitochondrial RNA polymerase (POLRMT) is distantly related to the bacteriophage T7 RNA polymerase and has the capacity to recognize promoter elements (14). In combination, POLRMT, TFAM, and the mammalian Mtf1 homolog TFB2M can initiate transcription from a promoter-containing DNA fragment in vitro (15). TFB2M forms a heterodimeric complex with POLRMT and in...

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mentioning

confidence: 64%

Mammalian transcription factor A is a core component of the mitochondrial transcription machinery

Shi

Dierckx

Wanrooij

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

167

150

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“…This protein has an additional role as an architectural protein, which is essential for the maintenance of mtDNA; therefore, it also serves as a limiting determinant for the mtDNA copy number 18, 19. Thus, the suppression of TFAM expression (Fig.…”

Section: Resultsmentioning

confidence: 99%

Linkage of E2F1 transcriptional network and cell proliferation with respiratory chain activity in breast cancer cells

et al. 2016

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Mitochondria are multifunctional organelles; they have been implicated in various aspects of tumorigenesis. In this study, we investigated a novel role of the basal electron transport chain (ETC) activity in cell proliferation by inhibiting mitochondrial replication and transcription (mtR/T) using pharmacological and genetic interventions, which depleted mitochondrial DNA/RNA, thereby inducing ETC deficiency. Interestingly, mtR/T inhibition did not decrease ATP levels despite deficiency in ETC activity in different cell types, including MDA‐MB‐231 breast cancer cells, but it severely impeded cell cycle progression, specifically progression during G2 and/or M phases in the cancer cells. Under these conditions, the expression of a group of cell cycle regulators was downregulated without affecting the growth signaling pathway. Further analysis suggested that the transcriptional network organized by E2F1 was significantly affected because of the downregulation of E2F1 in response to ETC deficiency, which eventually resulted in the suppression of cell proliferation. Thus, in this study, the E2F1‐mediated ETC‐dependent mechanism has emerged as the regulatory mechanism of cell cycle progression. In addition to E2F1, FOXM1 and BMYB were also downregulated, which contributed specifically to the defects in G2 and/or M phase progression. Thus, ETC‐deficient cancer cells lost their growing ability, including their tumorigenic potential in vivo. ETC deficiency abolished the production of reactive oxygen species (ROS) from the mitochondria and a mitochondria‐targeted antioxidant mimicked the deficiency, thereby suggesting that ETC activity signaled through ROS production. In conclusion, this novel coupling between ETC activity and cell cycle progression may be an important mechanism for coordinating cell proliferation and metabolism.

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“…For double fluorescent staining, the floating sections were stained with the following combinations of the first antibodies for 48 h at 4°C: anti- (Kanki et al, 2004b). After washing with PBS, the sections were incubated with a mixture of 0.5% Alexa 488 anti-mouse IgG and Cy3 anti-rabbit IgG, 0.5% Alexa 488 anti-rabbit IgG and Cy3 anti-mouse IgG (GE Healthcare) for 2 h at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Moreover, there is increasing evidence that TFAM plays an important role in maintaining mtDNA and regulating its copy number. The amount of mtDNA is closely correlated with the amount of TFAM but not with the transcription level, and the majority of TFAM molecules are involved in architecturally maintaining the higher structure of mtDNA (Kanki et al, 2004b). More recently, transgenic mice that overexpressed human TFAM under control of the ␤-actin promoter were generated and showed an increased copy number of mtDNA in the myocardium and the protection of the heart from mitochondrial dysfunction (Ikeuchi et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Reverse of Age-Dependent Memory Impairment and Mitochondrial DNA Damage in Microglia by an Overexpression of Human Mitochondrial Transcription Factor A in Mice

et al. 2008

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Mitochondrial DNA (mtDNA) is highly susceptible to injury induced by reactive oxygen species (ROS). During aging, mutations of mtDNA accumulate to induce dysfunction of the respiratory chain, resulting in the enhanced ROS production. Therefore, age-dependent memory impairment may result from oxidative stress derived from the respiratory chain. Mitochondrial transcription factor A (TFAM) is now known to have roles not only in the replication of mtDNA but also its maintenance. We herein report that an overexpression of TFAM in HeLa cells significantly inhibited rotenone-induced mitochondrial ROS generation and the subsequent NF-B (nuclear factor-B) nuclear translocation. Furthermore, TFAM transgenic (TG) mice exhibited a prominent amelioration of an age-dependent accumulation of lipid peroxidation products and a decline in the activities of complexes I and IV in the brain. In the aged TG mice, deficits of the motor learning memory, the working memory, and the hippocampal long-term potentiation (LTP) were also significantly improved. The expression level of interleukin-1␤ (IL-1␤) and mtDNA damages, which were predominantly found in microglia, significantly decreased in the aged TG mice. The IL-1␤ amount markedly increased in the brain of the TG mice after treatment with lipopolysaccharide (LPS), whereas its mean amount was significantly lower than that of the LPS-treated aged wild-type mice. At the same time, an increased mtDNA damage in microglia and an impaired hippocampal LTP were also observed in the LPS-treated aged TG mice. Together, an overexpression of TFAM is therefore considered to ameliorate age-dependent impairment of the brain functions through the prevention of oxidative stress and mitochondrial dysfunctions in microglia.

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Architectural Role of Mitochondrial Transcription Factor A in Maintenance of Human Mitochondrial DNA

Cited by 275 publications

References 43 publications

Mammalian transcription factor A is a core component of the mitochondrial transcription machinery

Mammalian transcription factor A is a core component of the mitochondrial transcription machinery

Linkage of E2F1 transcriptional network and cell proliferation with respiratory chain activity in breast cancer cells

Reverse of Age-Dependent Memory Impairment and Mitochondrial DNA Damage in Microglia by an Overexpression of Human Mitochondrial Transcription Factor A in Mice

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