Applied Force Reveals Mechanistic and Energetic Details of Transcription Termination

davidd submitted, created time 8 months 4 weeks (www.cell.com)

Transcription termination by bacterial RNA polymerase (RNAP) occurs at sequences coding for a GC-rich RNA hairpin followed by a U-rich tract. They used single-molecule techniques to investigate the mechanism by which three representative terminators (his, t500, and tR2) destabilize the elongation complex (EC). And they propose a quantitative, energetic model that predicts the behavior for these terminators and mutant variants.

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Dissociation of halted T7 RNA polymerase elongation complexes proceeds via a forward-translocation mechanism

annatto submitted, created time 1 year 7 months (www.pnas.org)

"A recent model for the mechanism of intrinsic transcription termination involves dissociation of the RNA from forward-translocated (hypertranslocated) states of the complex . The current study demonstrates that halted elongation complexes of T7 RNA polymerase in the absence of termination signals can also dissociate via a forward-translocation mechanism. Shortening of the downstream DNA or the introduction of a stretch of mismatched DNA immediately downstream of the halt site reduces a barrier to forward translocation and correspondingly reduces the lifetime of halted complexes

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RNA polymerase III transcription is repressed in response to the tumour suppressor ARF

addict submitted, created time 1 year 8 months (nar.oxfordjournals.org)

The tumour suppressor protein ARF provides a defence mechanism against hyperproliferative stresses that can result from the aberrant activation of oncogenes. ARF is silenced or deleted in many human cancers. Activation of ARF can arrest growth and cell cycle progression, or trigger apoptosis. A principle mediator of these effects is p53, which ARF stabilizes by binding and inhibiting MDM2. However, ARF has additional targets and remains able to block growth in the absence of p53, albeit less efficiently. For example, ARF can suppress rRNA production in a p53-independent manner

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Bacterial enhancer-binding proteins: unlocking σ54-dependent gene transcription

athena submitted, created time 1 year 8 months (www.sciencedirect.com)

"Bacterial transcription relies on the binding of dissociable sigma (σ) factors to RNA polymerase (RNAP) for promoter specificity. The major variant sigma factor (σ54) forms a stable closed complex with RNAP bound to DNA that rarely spontaneously isomerises to an open complex. ATP hydrolysis by bacterial enhancer-binding proteins is used to remodel the RNAP–σ54–DNA closed complex."

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Mitochondrial transcription and its regulation in mammalian cells

amanda submitted, created time 1 year 9 months (www.sciencedirect.com)

"Human mitochondria contain multiple copies of a small double-stranded DNA genome that encode 13 components of the electron-transport chain and RNA components that are needed for mitochondrial translation. The mitochondrial genome is transcribed by a specialized machinery that includes a monomeric RNA polymerase, the mitochondrial transcription factor A and one of the two mitochondrial transcription factor B paralogues, TFB1M or TFB2M. Today, the components of the basal transcription machinery in mammalian mitochondria are known and their mechanisms of action are gradually being established

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5'-Proximal Hot Spot for an Inducible Positive-to-Negative-Strand Template Switch by Coronavirus RNA-Dependent RNA Polymerase

julie submitted, created time 1 year 9 months (jvi.asm.org)

Coronaviruses have a positive-strand RNA genome and replicate through the use of a 3' nested set of subgenomic mRNAs each possessing a leader (65 to 90 nucleotides [nt] in length, depending on the viral species) identical to and derived from the genomic leader. One widely supported model for leader acquisition states that a template switch takes place during the generation of negative-strand antileader-containing templates used subsequently for subgenomic mRNA synthesis.

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RNA folding during transcription

biscuits submitted, created time 1 year 11 months (arjournals.annualreviews.org)

The evolution of RNA sequence needs to satisfy three requirements: folding, structure, and function. Understanding RNA folding during transcription requires the elucidation of structure formation and structural changes of the RNA, and the consideration of intrinsic properties of the RNA polymerase and other proteins that interact with the RNA. This review summarizes the research progress in this area and outlines the enormous challenges facing this field.

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