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An increase in mitochondrial DNA promotes nuclear DNA replication in yeast.

Blank HM, Li C, Mueller JE, Bogomolnaya LM, Bryk M, Polymenis M - PLoS Genet. (2008)

Bottom Line: The Sir2p NAD+-dependent de-acetylase antagonizes this mitochondrial role.We found that cells with increased mitochondrial DNA have reduced Sir2p levels bound at origins of DNA replication in the nucleus, accompanied with increased levels of K9, K14-acetylated histone H3 at those origins.They also suggest that cellular metabolism may impact on chromatin modifications to regulate the activity of origins of DNA replication.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America.

ABSTRACT
Coordination between cellular metabolism and DNA replication determines when cells initiate division. It has been assumed that metabolism only plays a permissive role in cell division. While blocking metabolism arrests cell division, it is not known whether an up-regulation of metabolic reactions accelerates cell cycle transitions. Here, we show that increasing the amount of mitochondrial DNA accelerates overall cell proliferation and promotes nuclear DNA replication, in a nutrient-dependent manner. The Sir2p NAD+-dependent de-acetylase antagonizes this mitochondrial role. We found that cells with increased mitochondrial DNA have reduced Sir2p levels bound at origins of DNA replication in the nucleus, accompanied with increased levels of K9, K14-acetylated histone H3 at those origins. Our results demonstrate an active role of mitochondrial processes in the control of cell division. They also suggest that cellular metabolism may impact on chromatin modifications to regulate the activity of origins of DNA replication.

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Cells moderately over-expressing ABF2 proliferate faster (A), and have altered cell cycle progression (B) in chemostat cultures.In A, a chemostat competition experiment done during glucose limitation at dilution rate D = 0.1 h−1 is shown. The specific growth differential (σ) between the two competing strains [41] is the average (±s.d.) of three independent competition experiments. In each experiment, and for each sampling point, the average (±s.d.) of at least three measurements was calculated. X3xABF2+(t) and XABF2+(t) represent the relative proportion of the two strains at time t, in generations. In B, cell cycle progression of the indicated strains and nutrient limitations was evaluated by flow cytometry. Cell numbers are plotted on the y-axis and fluorescence on the x-axis. The DNA content of cells in G1 and G2/M is indicated as 1C and 2C, respectively. The percentage of unbudded cells (%UB) correlates with G1 cells. The values shown are the average (±s.d.) of at least three independent experiments.
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pgen-1000047-g001: Cells moderately over-expressing ABF2 proliferate faster (A), and have altered cell cycle progression (B) in chemostat cultures.In A, a chemostat competition experiment done during glucose limitation at dilution rate D = 0.1 h−1 is shown. The specific growth differential (σ) between the two competing strains [41] is the average (±s.d.) of three independent competition experiments. In each experiment, and for each sampling point, the average (±s.d.) of at least three measurements was calculated. X3xABF2+(t) and XABF2+(t) represent the relative proportion of the two strains at time t, in generations. In B, cell cycle progression of the indicated strains and nutrient limitations was evaluated by flow cytometry. Cell numbers are plotted on the y-axis and fluorescence on the x-axis. The DNA content of cells in G1 and G2/M is indicated as 1C and 2C, respectively. The percentage of unbudded cells (%UB) correlates with G1 cells. The values shown are the average (±s.d.) of at least three independent experiments.

Mentions: We hypothesized that increasing the amount of mtDNA may mimic the situation of “evolved” yeast populations, which can proliferate faster than the parent population [2], allowing us to examine effects on cell division. We evaluated a strain (3xABF2+), which carries two additional copies of ABF2, because in this strain the amount of mtDNA is increased [9]. The 3xABF2+ strain proliferated faster than the wild type strain in glucose-limiting (0.08% glucose) conditions (Figure 1A), mimicking “evolved” strains [2]. We next examined cell cycle progression in defined chemostat cultures under glucose (Glc) or nitrogen (N) limitation at 0.2 h−1 dilution rate, D, comparing ABF2+ to 3xABF2+ cells (Figure 1B). Under Glc-limitation, the fraction of 3xABF2+ cells in G1 was reduced (Figure 1B, cells in G1, 53% 3xABF2+ compared to 61% ABF2+). In contrast, under N-limitation, extra copies of ABF2 did not affect the DNA content distribution in anabolically-restricted cells (Figure 1B, cells in G1, 52% 3xABF2+ compared to 51% ABF2+). These data suggest a connection between mitochondrial function and cell cycle progression that is evident under glucose limitation in cells over-expressing ABF2. Interestingly, 3xABF2+ cells are the same size as wild type cells (Figure 2A), possibly explaining why ABF2 mutations were not identified previously in size-based mutant screens for cell cycle regulators.


An increase in mitochondrial DNA promotes nuclear DNA replication in yeast.

Blank HM, Li C, Mueller JE, Bogomolnaya LM, Bryk M, Polymenis M - PLoS Genet. (2008)

Cells moderately over-expressing ABF2 proliferate faster (A), and have altered cell cycle progression (B) in chemostat cultures.In A, a chemostat competition experiment done during glucose limitation at dilution rate D = 0.1 h−1 is shown. The specific growth differential (σ) between the two competing strains [41] is the average (±s.d.) of three independent competition experiments. In each experiment, and for each sampling point, the average (±s.d.) of at least three measurements was calculated. X3xABF2+(t) and XABF2+(t) represent the relative proportion of the two strains at time t, in generations. In B, cell cycle progression of the indicated strains and nutrient limitations was evaluated by flow cytometry. Cell numbers are plotted on the y-axis and fluorescence on the x-axis. The DNA content of cells in G1 and G2/M is indicated as 1C and 2C, respectively. The percentage of unbudded cells (%UB) correlates with G1 cells. The values shown are the average (±s.d.) of at least three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2289842&req=5

pgen-1000047-g001: Cells moderately over-expressing ABF2 proliferate faster (A), and have altered cell cycle progression (B) in chemostat cultures.In A, a chemostat competition experiment done during glucose limitation at dilution rate D = 0.1 h−1 is shown. The specific growth differential (σ) between the two competing strains [41] is the average (±s.d.) of three independent competition experiments. In each experiment, and for each sampling point, the average (±s.d.) of at least three measurements was calculated. X3xABF2+(t) and XABF2+(t) represent the relative proportion of the two strains at time t, in generations. In B, cell cycle progression of the indicated strains and nutrient limitations was evaluated by flow cytometry. Cell numbers are plotted on the y-axis and fluorescence on the x-axis. The DNA content of cells in G1 and G2/M is indicated as 1C and 2C, respectively. The percentage of unbudded cells (%UB) correlates with G1 cells. The values shown are the average (±s.d.) of at least three independent experiments.
Mentions: We hypothesized that increasing the amount of mtDNA may mimic the situation of “evolved” yeast populations, which can proliferate faster than the parent population [2], allowing us to examine effects on cell division. We evaluated a strain (3xABF2+), which carries two additional copies of ABF2, because in this strain the amount of mtDNA is increased [9]. The 3xABF2+ strain proliferated faster than the wild type strain in glucose-limiting (0.08% glucose) conditions (Figure 1A), mimicking “evolved” strains [2]. We next examined cell cycle progression in defined chemostat cultures under glucose (Glc) or nitrogen (N) limitation at 0.2 h−1 dilution rate, D, comparing ABF2+ to 3xABF2+ cells (Figure 1B). Under Glc-limitation, the fraction of 3xABF2+ cells in G1 was reduced (Figure 1B, cells in G1, 53% 3xABF2+ compared to 61% ABF2+). In contrast, under N-limitation, extra copies of ABF2 did not affect the DNA content distribution in anabolically-restricted cells (Figure 1B, cells in G1, 52% 3xABF2+ compared to 51% ABF2+). These data suggest a connection between mitochondrial function and cell cycle progression that is evident under glucose limitation in cells over-expressing ABF2. Interestingly, 3xABF2+ cells are the same size as wild type cells (Figure 2A), possibly explaining why ABF2 mutations were not identified previously in size-based mutant screens for cell cycle regulators.

Bottom Line: The Sir2p NAD+-dependent de-acetylase antagonizes this mitochondrial role.We found that cells with increased mitochondrial DNA have reduced Sir2p levels bound at origins of DNA replication in the nucleus, accompanied with increased levels of K9, K14-acetylated histone H3 at those origins.They also suggest that cellular metabolism may impact on chromatin modifications to regulate the activity of origins of DNA replication.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America.

ABSTRACT
Coordination between cellular metabolism and DNA replication determines when cells initiate division. It has been assumed that metabolism only plays a permissive role in cell division. While blocking metabolism arrests cell division, it is not known whether an up-regulation of metabolic reactions accelerates cell cycle transitions. Here, we show that increasing the amount of mitochondrial DNA accelerates overall cell proliferation and promotes nuclear DNA replication, in a nutrient-dependent manner. The Sir2p NAD+-dependent de-acetylase antagonizes this mitochondrial role. We found that cells with increased mitochondrial DNA have reduced Sir2p levels bound at origins of DNA replication in the nucleus, accompanied with increased levels of K9, K14-acetylated histone H3 at those origins. Our results demonstrate an active role of mitochondrial processes in the control of cell division. They also suggest that cellular metabolism may impact on chromatin modifications to regulate the activity of origins of DNA replication.

Show MeSH
Related in: MedlinePlus