Transcription of functionally related constitutive genes is not coordinated

Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
Nature Structural & Molecular Biology (Impact Factor: 13.31). 01/2011; 18(1):27-34. DOI: 10.1038/nsmb.1934
Source: PubMed


Expression of an individual gene can vary considerably among genetically identical cells because of stochastic fluctuations in transcription. However, proteins comprising essential complexes or pathways have similar abundances and lower variability. It is not known whether coordination in the expression of subunits of essential complexes occurs at the level of transcription, mRNA abundance or protein expression. To directly measure the level of coordination in the expression of genes, we used highly sensitive fluorescence in situ hybridization (FISH) to count individual mRNAs of functionally related and unrelated genes within single Saccharomyces cerevisiae cells. Our results revealed that transcript levels of temporally induced genes are highly correlated in individual cells. In contrast, transcription of constitutive genes encoding essential subunits of complexes is not coordinated because of stochastic fluctuations. The coordination of these functional complexes therefore must occur post-transcriptionally, and likely post-translationally.

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    • "Conversely , at category II promoters, where Rap1 binds much closer to Fhl1 and Hmo1 is not present, we propose that Rap1 interacts directly with Fhl1 and/or Ifh1, consistent with recently reported in vitro binding studies (Mallick and Whiteway 2013). Rap1 may also support Fhl1/Ifh1 and Hmo1 binding through a still poorly understood ability to exclude nucleosomes in its vicinity (Gandhi et al. 2011). "
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    • "Regulated genes tend to show large variability in expression between individual cells, resulting in an asymmetric or skewed distribution curve for a given cell population [3], [4]. By contrast, genes expressed at a steady-state show lower variability which result in a Poisson distribution curve as in the case of yeast housekeeping genes that are constitutively active [5], [6]. The increased transcriptional variability associated with regulated genes compared to that of constitutively active genes is predicted to be due to infrequent but intense episodes or ‘bursts’ of transcriptional activity [6], [7]. "
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    PLoS ONE 09/2013; 8(9):e76043. DOI:10.1371/journal.pone.0076043 · 3.23 Impact Factor
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    • "Trcek et al. reported that CLB2 mRNA decay is primed with CLB2 promoter-associated proteins and suggested that regulated mRNA decay implicates the CCR4-NOT complex (Trcek et al., 2011). Consistent with this hypothesis, we found that expression of CLB2 transcripts under the ACT1 promoter resulted in unregulated accumulation under all conditions with the exception of the typical drop in copy number following cell division (Figure 2D) (Gandhi et al., 2011). ACT1 message number itself does not drop following cell division, typical of what has been observed in previous studies (Pramila et al., 2006). "
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