Stochastic transcription in the p53-mediated response to DNA damage is modulated by burst frequency (2019)
Figure 5

Figure 5 - The interplay of p53's C-terminal lysine acetylation and methylation regulates transiently expressed target genes in response to IR.

A A schematic illustration of p53's C-terminal modifications and described functional implications, including key regulatory enzymes.

B Total p53, p53 acetylated at K382 and K370 as well as GAPDH were measured by Western Blot at indicated time points in the context of different p53 dynamics: pulsing p53 (10 Gy IR), transient p53 (10 Gy IR + BML-277, central lanes) and sustained p53 (10 Gy IR + Nutlin-3, right lanes). See Figure 3 and Methods section for details.

C The relative change in p53 acetylation at K370 (light green) and K382 (dark green) was quantified from Western Blot and normalized to the abundance 3 h post IR. Means and propagated standard errors from 3 independent experiments are indicated. Acetylation increased over time in the context of sustained p53. See also Appendix Fig S12.

D The p53-K370 methylase Smyd2 was down-regulated in a clonal stable A549 cell line expressing a corresponding shRNA. Transcript levels were measured in wild type and knockdown cells by qRT-PCR. Mean levels and standard deviation from technical triplicates are indicated.

E/F Promoter activity of CDKN1A (E) and MDM2 (F) were quantified in Smyd2 knockdown cells before (basal, grey) and 3 h (red), 6 h (blue) and 9 h (orange) after DNA damage (10 Gy IR). Left panel: The percentage of cells with active TSS, subdivided into populations with strong (> 75% of TSS, solid colors) and weak (<75% of TSS, shaded colors) activity, is shown as stacked bar graphs, the mean fraction of active promoters is indicated above each bar. Right panel: Distributions of calculated transcription rates at active TSS are presented for each time point as probability density estimates (PDF, see Data Visualization section). We measured a higher fraction of active promoters upon damage compared to A549 wild type cells (Fig 3), while transcription rates remained unchanged. See Fig EV5A for corresponding changes in p53 acetylation patterns.

G The p53-K382 methylase Set8 was down-regulated in a clonal stable A549 cell line expressing a corresponding shRNA. Transcript levels were measured in wild type and knockdown cells by qRT-PCR. Mean levels and standard deviation from technical triplicates are indicated.

H/I Promoter activity of CDKN1A (E) and MDM2 (F) were quantified in Set8 knock-down cells before (basal, grey) and 3 h (red), 6 h (blue) and 9 h (orange) after DNA damage (10 Gy IR). Left panel: The percentage of cells with active TSS, subdivided into populations with strong (> 75% of TSS, solid colors) and weak (<75% of TSS, shaded colors) activity, is shown as stacked bar graphs, the mean fraction of active promoters is indicated above each bar. Right panel: Distributions of calculated transcription rates at active TSS are presented for each time point as probability density estimates (PDF, see Data Visualization section). We measured a higher fraction of active promoters upon damage compared to A549 wild type cells (Figure 3), while transcription rates remained unchanged. See Fig EV5A for corresponding changes in p53 acetylation patterns.