The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform

John W. Tamkun - One of the best experts on this subject based on the ideXlab platform.

  • Stalled polymerases and transcriptional regulation
    Nature Genetics, 2007
    Co-Authors: John W. Tamkun
    Abstract:

    This is an issue edsumm for 1421. Identification of the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence shows that sea surface temperatures near the North Pole increased from roughly 18 degrees Celsius to over 23 degrees Celsius — such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. After initiating transcription, RNA polymerase II often stalls a short Distance Downstream of promoters. The recent discovery of stalled polymerases at a large number of eukaryotic promoters suggests that the regulation of stalling plays a more important role in gene expression and development than previously suspected.

  • Stalled polymerases and transcriptional regulation.
    Nature genetics, 2007
    Co-Authors: John W. Tamkun
    Abstract:

    After initiating transcription, RNA polymerase II often stalls a short Distance Downstream of promoters. The recent discovery of stalled polymerases at a large number of eukaryotic promoters suggests that the regulation of stalling plays a more important role in gene expression and development than previously suspected.

Hiroji Aiba - One of the best experts on this subject based on the ideXlab platform.

  • Regulation of intrinsic terminator by translation in Escherichia coli: transcription termination at a Distance Downstream.
    Genes to Cells, 1999
    Co-Authors: Hiroji Aiba
    Abstract:

    Background: Rho-independent terminators in Escherichia coli are DNA sequences of 30–50 bp consisting of a GC-rich dyad symmetry sequence followed by a run of T residues in the nontemplate strand. The transcription termination at the Rho-independent terminator occurs within the T-tract in vitro. It has been believed that the transcription termination at the Rho-independent terminator occurs within the T-tract in vivo, as established in vitro, and therefore the 3′ ends of mRNAs are mostly generated as a direct result of transcription termination. However, how the transcription termination occurs and how the 3′ ends of mRNAs are formed in living cells remains to be studied. Results: We developed a double terminator system in which a second Rho-independent terminator was placed Downstream of the crp terminator. This system made it possible to detect transcripts that pass through the crp terminator by Northern blotting. We found that most of the crp transcripts extend beyond the crp terminator. The transcriptional read-through at the crp terminator was reduced when the translation of crp mRNA was interrupted. The level of the read-through transcript decreased with Distance between the two terminators, suggesting that transcription termination occurs at multiple positions beyond the crp terminator. Conclusion: We conclude that most RNA polymerase reads through the crp terminator in the natural situation and terminates transcription over a wide region Downstream of the crp terminator, resulting in heterogeneous primary transcripts that are subsequently processed back to the terminator hairpin. We propose that ribosome translation to the crp stop codon causes read-through of the terminator. The regulatory effect of translation on Rho-independent termination may be a general phenomenon at other operons.

Gerald L. Feder - One of the best experts on this subject based on the ideXlab platform.

  • Humic substances and trace metals associated with Fe and Al oxides deposited in an acidic mountain stream
    Science of The Total Environment, 1992
    Co-Authors: Diane M. Mcknight, Robert L. Wershaw, Kenneth E. Bencala, Gary W. Zellweger, Gerald L. Feder
    Abstract:

    Hydrous iron and aluminum oxides are deposited on the streambed in the confluence of the Snake River and Deer Creek, two streams in the Colorado Rocky Mountains. The Snake River is acidic and has high concentrations of dissolved Fe and Al. These metals precipitate at the confluence with the pristine, neutral pH, Deer Creek because of the greater pH (4.5–6.0) in the confluence. The composition of the deposited oxides changes consistently with Distance Downstream, with the most upstream oxide samples having the greatest Fe and organic carbon content. Fulvic acid accounts for most of the organic content of the oxides. Results indicate that streambed oxides in the confluence are not saturated with respect to their capacity to sorb dissolved humic substances from streamwater. The contents of several trace metals (Mn, Zn, Cu, Pb, Ni and Co) also decrease with Distance Downstream and are correlated with both the Fe and organic carbon contents. Strong metal-binding sites associated with the sorbed fulvic acid are more than sufficient to account for the trace metal content of the oxides. Complexation of trace metals by sorbed fulvic acid may explain the observed Downstream decrease in trace metal content.

Diane M. Mcknight - One of the best experts on this subject based on the ideXlab platform.

  • Humic substances and trace metals associated with Fe and Al oxides deposited in an acidic mountain stream
    Science of The Total Environment, 1992
    Co-Authors: Diane M. Mcknight, Robert L. Wershaw, Kenneth E. Bencala, Gary W. Zellweger, Gerald L. Feder
    Abstract:

    Hydrous iron and aluminum oxides are deposited on the streambed in the confluence of the Snake River and Deer Creek, two streams in the Colorado Rocky Mountains. The Snake River is acidic and has high concentrations of dissolved Fe and Al. These metals precipitate at the confluence with the pristine, neutral pH, Deer Creek because of the greater pH (4.5–6.0) in the confluence. The composition of the deposited oxides changes consistently with Distance Downstream, with the most upstream oxide samples having the greatest Fe and organic carbon content. Fulvic acid accounts for most of the organic content of the oxides. Results indicate that streambed oxides in the confluence are not saturated with respect to their capacity to sorb dissolved humic substances from streamwater. The contents of several trace metals (Mn, Zn, Cu, Pb, Ni and Co) also decrease with Distance Downstream and are correlated with both the Fe and organic carbon contents. Strong metal-binding sites associated with the sorbed fulvic acid are more than sufficient to account for the trace metal content of the oxides. Complexation of trace metals by sorbed fulvic acid may explain the observed Downstream decrease in trace metal content.

Philip Hall - One of the best experts on this subject based on the ideXlab platform.

  • The Nonlinear Evolution of the Inviscid Secondary Instability of Streamwise Vortex Structures
    Philosophical Transactions of the Royal Society of London. Series A: Physical and Engineering Sciences, 1995
    Co-Authors: N. D. Blackaby, Philip Hall
    Abstract:

    The weakly nonlinear evolution of an inviscid marginally unstable wave growing on a boundary layer supporting a streamwise vortex structure is investigated. The nonlinear growth of the wave is found to be controlled by the diffusion layer located at the edge of the critical layer associated with the wave. The evolution equation is found to depend on the upstream history of the wave and the solution of the equation suggests th at the wave either restructures the mean state so as to make it stable or develops a singularity at a finite Distance Downstream of the point of neutral stability.