Dataset Information

Processivity and coupling in messenger RNA transcription.

ABSTRACT:

Background

The complexity of messenger RNA processing is now being uncovered by experimental techniques that are capable of detecting individual copies of mRNA in cells, and by quantitative real-time observations that reveal the kinetics. This processing is commonly modelled by permitting mRNA to be transcribed only when the promoter is in the on state. In this simple on/off model, the many processes involved in active transcription are represented by a single reaction. These processes include elongation, which has a minimum time for completion and processing that is not captured in the model.

Methodology

In this paper, we explore the impact on the mRNA distribution of representing the elongation process in more detail. Consideration of the mechanisms of elongation leads to two alternative models of the coupling between the elongating polymerase and the state of the promoter: Processivity allows polymerases to complete elongation irrespective of the promoter state, whereas coupling requires the promoter to be active to produce a full-length transcript. We demonstrate that these alternatives have a significant impact on the predicted distributions. Models are simulated by the Gillespie algorithm, and the third and fourth moments of the resulting distribution are computed in order to characterise the length of the tail, and sharpness of the peak. By this methodology, we show that the moments provide a concise summary of the distribution, showing statistically-significant differences across much of the feasible parameter range.

Conclusions

We conclude that processivity is not fully consistent with the on/off model unless the probability of successfully completing elongation is low--as has been observed. The results also suggest that some form of coupling between the promoter and a rate-limiting step in transcription may explain the cell's inability to maintain high mRNA levels at low noise--a prediction of the on/off model that has no supporting evidence.

SUBMITTER: Aitken S

PROVIDER: S-EPMC2812496 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Publications

Processivity and coupling in messenger RNA transcription.

Aitken Stuart S Robert Marie-Cécile MC Alexander Ross D RD Goryanin Igor I Bertrand Edouard E Beggs Jean D JD

PloS one 20100128 1

<h4>Background</h4>The complexity of messenger RNA processing is now being uncovered by experimental techniques that are capable of detecting individual copies of mRNA in cells, and by quantitative real-time observations that reveal the kinetics. This processing is commonly modelled by permitting mRNA to be transcribed only when the promoter is in the on state. In this simple on/off model, the many processes involved in active transcription are represented by a single reaction. These processes i ...[more]

PMID: 20126621

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Project description:Elongin is an RNA polymerase II (RNAPII)-associated factor that has been shown to stimulate transcriptional elongation in vitro. The Elongin complex is thought to be required for transcriptional induction in response to cellular stimuli and to ubiquitinate RNAPII in response to DNA damage. Yet the impact of the Elongin complex on transcription in vivo has not been well studied. Here, we performed comprehensive studies of the role of Elongin A, the largest subunit of the Elongin complex, on RNAPII transcription genome-wide. In an effort to explore regulatory roles for Elongin A, we performed IP-MS. We constructed a DLD1 cell line expressing Flag-tagged Elongin A at endogenous levels and performed anti-Flag immuno-purification of solubilized chromatin followed by analysis of binding partners by mass spectrometry in triplicates. We identified a large group of Elongin A-associated proteins. We confirmed a subset of possible interacting proteins by Co-IP and western blotting. Consistent with previous studies, we identified RNA Pol II subunits and proteins related to transcription elongation and RNA processing. Among the top hits, we identified nearly all subunits of the PAF1 complex, except for RTF1, which does not stably associate with mammalian PAF1. Concordantly, in our previous PAF1 proteomic study, Elongin A was also among the top hits. We also identified several subunits of the Integrator complex, a multi-subunit complex that has been shown to participate in enhancer RNA (eRNA) processing, a finding consistent with our conclusion that Elongin A localizes to potential enhancers. Collectively, our results suggest that Elongin A stably interacts with RNAPII and the transcription machinery on chromatin. Taken together, our studies suggest that Elongin A associates with the transcription machinery at actively transcribed genomic regions and may be involved in the release of paused RNAPII. However, Elongin A does not appear to be critical for maintaining transcription elongation rates in vivo.

Dataset Information

Processivity and coupling in messenger RNA transcription.

Background

Methodology

Conclusions

Publications

Processivity and coupling in messenger RNA transcription.

Similar Datasets

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