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Reliable cell cycle commitment in budding yeast is ensured by signal integration.

Liu X, Wang X, Yang X, Liu S, Jiang L, Qu Y, Hu L, Ouyang Q, Tang C - Elife (2015)

Bottom Line: We further identify the Start repressor, Whi5, as the integrator.The instantaneous kinase activity of Cln3-Cdk1 is recorded over time on the phosphorylated Whi5, and the decision is made only when phosphorylated Whi5 reaches a threshold.Our work shows that the strategy of signal integration, which was previously found in decision-making behaviors of animals, is adopted at the cellular level to reduce noise and minimize uncertainty.

View Article: PubMed Central - PubMed

Affiliation: Center for Quantitative Biology, Peking University, Beijing, China.

ABSTRACT
Cell fate decisions are critical for life, yet little is known about how their reliability is achieved when signals are noisy and fluctuating with time. In this study, we show that in budding yeast, the decision of cell cycle commitment (Start) is determined by the time integration of its triggering signal Cln3. We further identify the Start repressor, Whi5, as the integrator. The instantaneous kinase activity of Cln3-Cdk1 is recorded over time on the phosphorylated Whi5, and the decision is made only when phosphorylated Whi5 reaches a threshold. Cells adjust the threshold by modulating Whi5 concentration in different nutrient conditions to coordinate growth and division. Our work shows that the strategy of signal integration, which was previously found in decision-making behaviors of animals, is adopted at the cellular level to reduce noise and minimize uncertainty.

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Related in: MedlinePlus

The promoter GlacSpr is repressed by LacI and inducedby IPTG.(A) The sequence of GlacSpr. (B)The dose–response curve of GlacSpr. Thetranscriptional activity of GlacSpr in the OFF state is alittle higher than GAL1pr in glucose, as the result,GlacSpr is not tight enough to completely shut off thecyclin activity of the wild-type Cln3. The cln3Δbck2Δ cells carrying GlacSpr-CLN3 areviable in the absence of IPTG with prolonged G1 phase.DOI:http://dx.doi.org/10.7554/eLife.03977.005
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fig1s2: The promoter GlacSpr is repressed by LacI and inducedby IPTG.(A) The sequence of GlacSpr. (B)The dose–response curve of GlacSpr. Thetranscriptional activity of GlacSpr in the OFF state is alittle higher than GAL1pr in glucose, as the result,GlacSpr is not tight enough to completely shut off thecyclin activity of the wild-type Cln3. The cln3Δbck2Δ cells carrying GlacSpr-CLN3 areviable in the absence of IPTG with prolonged G1 phase.DOI:http://dx.doi.org/10.7554/eLife.03977.005

Mentions: To quantitatively investigate how Start transition is triggered by Cln3, we firstintegrated a copy of inducible CLN3 onto the genome in a strainlacking the native CLN3 and BCK2 and fused theendogenous WHI5 with the red fluorescent protein tdTomato. The G1length TG1 is defined as the timeinterval between Whi5 nuclear entry in late mitosis and its exclusion from thenucleus at the Start transition (Taberner et al.,2009) (Figure 1B and Figure 1—figure supplement 1), which isa measure for how long the cell waits to make the Start decision. Cln3 level under asynthetic inducible promoter GlacSpr (Figure 1—figure supplement 2) was controlled bytitrating the inducer IPTG. The cells were grown in a microfluidic chip and monitoredby time-lapse microscopy. We found that in both mother and daughter cells G1 lengthis prolonged as IPTG concentration decreases, which is consistent with the previousfindings that increased Cln3 dosage shortens G1 length (Di Talia et al., 2007) and suggests a negative correlationbetween G1 length and Cln3 level (Figure1C).


Reliable cell cycle commitment in budding yeast is ensured by signal integration.

Liu X, Wang X, Yang X, Liu S, Jiang L, Qu Y, Hu L, Ouyang Q, Tang C - Elife (2015)

The promoter GlacSpr is repressed by LacI and inducedby IPTG.(A) The sequence of GlacSpr. (B)The dose–response curve of GlacSpr. Thetranscriptional activity of GlacSpr in the OFF state is alittle higher than GAL1pr in glucose, as the result,GlacSpr is not tight enough to completely shut off thecyclin activity of the wild-type Cln3. The cln3Δbck2Δ cells carrying GlacSpr-CLN3 areviable in the absence of IPTG with prolonged G1 phase.DOI:http://dx.doi.org/10.7554/eLife.03977.005
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4378612&req=5

fig1s2: The promoter GlacSpr is repressed by LacI and inducedby IPTG.(A) The sequence of GlacSpr. (B)The dose–response curve of GlacSpr. Thetranscriptional activity of GlacSpr in the OFF state is alittle higher than GAL1pr in glucose, as the result,GlacSpr is not tight enough to completely shut off thecyclin activity of the wild-type Cln3. The cln3Δbck2Δ cells carrying GlacSpr-CLN3 areviable in the absence of IPTG with prolonged G1 phase.DOI:http://dx.doi.org/10.7554/eLife.03977.005
Mentions: To quantitatively investigate how Start transition is triggered by Cln3, we firstintegrated a copy of inducible CLN3 onto the genome in a strainlacking the native CLN3 and BCK2 and fused theendogenous WHI5 with the red fluorescent protein tdTomato. The G1length TG1 is defined as the timeinterval between Whi5 nuclear entry in late mitosis and its exclusion from thenucleus at the Start transition (Taberner et al.,2009) (Figure 1B and Figure 1—figure supplement 1), which isa measure for how long the cell waits to make the Start decision. Cln3 level under asynthetic inducible promoter GlacSpr (Figure 1—figure supplement 2) was controlled bytitrating the inducer IPTG. The cells were grown in a microfluidic chip and monitoredby time-lapse microscopy. We found that in both mother and daughter cells G1 lengthis prolonged as IPTG concentration decreases, which is consistent with the previousfindings that increased Cln3 dosage shortens G1 length (Di Talia et al., 2007) and suggests a negative correlationbetween G1 length and Cln3 level (Figure1C).

Bottom Line: We further identify the Start repressor, Whi5, as the integrator.The instantaneous kinase activity of Cln3-Cdk1 is recorded over time on the phosphorylated Whi5, and the decision is made only when phosphorylated Whi5 reaches a threshold.Our work shows that the strategy of signal integration, which was previously found in decision-making behaviors of animals, is adopted at the cellular level to reduce noise and minimize uncertainty.

View Article: PubMed Central - PubMed

Affiliation: Center for Quantitative Biology, Peking University, Beijing, China.

ABSTRACT
Cell fate decisions are critical for life, yet little is known about how their reliability is achieved when signals are noisy and fluctuating with time. In this study, we show that in budding yeast, the decision of cell cycle commitment (Start) is determined by the time integration of its triggering signal Cln3. We further identify the Start repressor, Whi5, as the integrator. The instantaneous kinase activity of Cln3-Cdk1 is recorded over time on the phosphorylated Whi5, and the decision is made only when phosphorylated Whi5 reaches a threshold. Cells adjust the threshold by modulating Whi5 concentration in different nutrient conditions to coordinate growth and division. Our work shows that the strategy of signal integration, which was previously found in decision-making behaviors of animals, is adopted at the cellular level to reduce noise and minimize uncertainty.

Show MeSH
Related in: MedlinePlus