A novel intermediate in transcription initiation by human mitochondrial RNA polymerase

The mitochondrial genome is transcribed by a single-subunit T7 phage-like RNA polymerase (mtRNAP),structurally unrelated to cellular RNAPs. In higher eukaryotes, mtRNAP requires two transcription factors for efficient initiation-TFAM, a major nucleoid protein, and TFB2M, a transient component of mtRNAP catalytic site. The mechanisms behind assembly of the mitochondrial transcription machinery and its regulation are poorly understood. We isolated and identified a previously unknown human mitochondrial transcription intermediate-a pre-initiation complex that includes mtRNAP, TFAM and promoter DNA. Using protein-protein cross-linking, we demonstrate that human TFAM binds to the N-terminal domain of mtRNAP, which results in bending of the promoter DNA around mtRNAP. The subsequent recruitment of TFB2M induces promoter melting and formation of an open initiation complex. Our data indicate that the pre-initiation complex is likely to be an important target for transcription regulation and provide basis for further structural, biochemical and biophysical studies of mitochondrial transcription

Mechanisms of mitochondrial promoter recognition in humans and other mammalian species

Recognition of mammalian mitochondrial promoters requires the concerted action of mitochondrial RNA polymerase (mtRNAP) and transcription initiation factors TFAM and TFB2M. In this work, we found that transcript slippage results in heterogeneity of the human mitochondrial transcripts in vivo and in vitro. This allowed us to correctly interpret the RNAseq data, identify the bona fide transcription start sites (TSS), and assign mitochondrial promoters for \u3e 50% of mammalian species and some other vertebrates. The divergent structure of the mammalian promoters reveals previously unappreciated aspects of mtDNA evolution. The correct assignment of TSS also enabled us to establish the precise register of the DNA in the initiation complex and permitted investigation of the sequence-specific protein-DNA interactions. We determined the molecular basis of promoter recognition by mtRNAP and TFB2M, which cooperatively recognize bases near TSS in a species-specific manner. Our findings reveal a role of mitochondrial transcription machinery in mitonuclear coevolution and speciation

Mechanism of Transcription Anti-termination in Human Mitochondria.

In human mitochondria, transcription termination events at a G-quadruplex region near the replication origin are thought to drive replication of mtDNA by generation of an RNA primer. This process is suppressed by a key regulator of mtDNA-the transcription factor TEFM. We determined the structure of an anti-termination complex in which TEFM is bound to transcribing mtRNAP. The structure reveals interactions of the dimeric pseudonuclease core of TEFM with mobile structural elements in mtRNAP and the nucleic acid components of the elongation complex (EC). Binding of TEFM to the DNA forms a downstream sliding clamp, providing high processivity to the EC. TEFM also binds near the RNA exit channel to prevent formation of the RNA G-quadruplex structure required for termination and thus synthesis of the replication primer. Our data provide insights into target specificity of TEFM and mechanisms by which it regulates the switch between transcription and replication of mtDNA

Mathematical Modeling of the Impact of Anode Bottom Problems of the Anode Current Distribution High Current Electrolyzer

В статье представлены результаты математического моделирования тепловых и электрических полей в электролизерах РА-400 и РА-550 при различных по высоте «конусах» и месту расположения, образованных на подошве анодов. Показано хорошее согласование расчетных и экспериментальных данных. Определены критерии для наиболее раннего обнаружения «конусов»The article presents the results of mathematical modeling of thermal and electric fields in the electrolyzer RA-400 and RA-550 at different height “cones” and the location formed at the base of the anodes. Received good agreement between the calculated and experimental data. Criteria for the earliest detection “cones” were founde

Electrical Resistance Preheating of High-Amperage Cells

На текущий момент нет единого мнения о том, какой способ обжига лучше. В большинстве случаев выбор того или иного способа на каждом алюминиевом заводе определяется рядом объективных и субъективных факторов. Зачастую при выборе способа обжига не учитываются затраты на использование энергии на этот процесс (электрической или от сжигания эквивалентного количества различных видов топлива), что может иметь существенное значение для различных регионов и влиять на себестоимость выпускаемого алюминия. В данной статье представлены результаты испытаний электрического обжига электролизеров опытного участка РА-400 ОАО «РУСАЛ Саяногорск»At present, there is no single opinion on which cell preheating method is best. In most cases, such a method (that is to be chosen for a smelter) is chosen based on a number of objective and subjective factors. It is often when a method is chosen that power expenses (either electricity or power generated from fuel combustion) for such a method are not taken into account. However, it can play a crucial role for different regions and influence the production cost of Al. This paper discusses the results of testing the method of electrical preheating in a pilot cell area (RA-400 cells) at OJSC RUSAL Sayanogors

Mechanism of Transcription Anti-termination in Human Mitochondria

In human mitochondria, transcription termination events at a G-quadruplex region near the replication origin are thought to drive replication of mtDNA by generation of an RNA primer. This process is suppressed by a key regulator of mtDNA—the transcription factor TEFM. We determined the structure of an anti-termination complex in which TEFM is bound to transcribing mtRNAP. The structure reveals interactions of the dimeric pseudonuclease core of TEFM with mobile structural elements in mtRNAP and the nucleic acid components of the elongation complex (EC). Binding of TEFM to the DNA forms a downstream “sliding clamp,” providing high processivity to the EC. TEFM also binds near the RNA exit channel to prevent formation of the RNA G-quadruplex structure required for termination and thus synthesis of the replication primer. Our data provide insights into target specificity of TEFM and mechanisms by which it regulates the switch between transcription and replication of mtDNA

Mathematical Modeling of the Impact of Anode Bottom Problems of the Anode Current Distribution High Current Electrolyzer

В статье представлены результаты математического моделирования тепловых и электрических полей в электролизерах РА-400 и РА-550 при различных по высоте «конусах» и месту расположения, образованных на подошве анодов. Показано хорошее согласование расчетных и экспериментальных данных. Определены критерии для наиболее раннего обнаружения «конусов»The article presents the results of mathematical modeling of thermal and electric fields in the electrolyzer RA-400 and RA-550 at different height “cones” and the location formed at the base of the anodes. Received good agreement between the calculated and experimental data. Criteria for the earliest detection “cones” were founde

Electrical Resistance Preheating of High-Amperage Cells

На текущий момент нет единого мнения о том, какой способ обжига лучше. В большинстве случаев выбор того или иного способа на каждом алюминиевом заводе определяется рядом объективных и субъективных факторов. Зачастую при выборе способа обжига не учитываются затраты на использование энергии на этот процесс (электрической или от сжигания эквивалентного количества различных видов топлива), что может иметь существенное значение для различных регионов и влиять на себестоимость выпускаемого алюминия. В данной статье представлены результаты испытаний электрического обжига электролизеров опытного участка РА-400 ОАО «РУСАЛ Саяногорск»At present, there is no single opinion on which cell preheating method is best. In most cases, such a method (that is to be chosen for a smelter) is chosen based on a number of objective and subjective factors. It is often when a method is chosen that power expenses (either electricity or power generated from fuel combustion) for such a method are not taken into account. However, it can play a crucial role for different regions and influence the production cost of Al. This paper discusses the results of testing the method of electrical preheating in a pilot cell area (RA-400 cells) at OJSC RUSAL Sayanogors

A model for transcription initiation in human mitochondria

Regulation of transcription of mtDNA is thought to be crucial for maintenance of redox potential and vitality of the cell but is poorly understood at the molecular level. In this study we mapped the binding sites of the core transcription initiation factors TFAM and TFB2M on human mitochondrial RNA polymerase, and interactions of the latter with promoter DNA. This allowed us to construct a detailed structural model, which displays a remarkable level of interaction between the components of the initiation complex (IC). The architecture of the mitochondrial IC suggests mechanisms of promoter binding and recognition that are distinct from the mechanisms found in RNAPs operating in all domains of life, and illuminates strategies of transcription regulation developed at the very early stages of evolution of gene expression