Fig. 5

PRRG4 regulates the expression of mitochondrial DNA polymerase POLG through STAT3. A Knockdown of PRRG4 reduces the mRNA level of POLG in SKBR3 and SUM149PT cells. Relative mRNA levels of POLG were analyzed by qRT-PCR. B Knockdown of PRRG4 inhibits POLG protein levels in SKBR3 and SUM149PT cells. C PRRG4 overexpression enhances POLG protein levels through STAT3 activation in MDA-MB-231 and HCC1954 cells. Cells with PRRG4-WT were treated with vehicle or Stattic (3 µM for MDA-MB-231, and 2 µM for HCC1954 cells) for 20 h. D Overexpression of a dominant negative STAT3 mutant (STAT3-DN) reduces POLG protein levels in SUM149PT cells. POLG and p-Stat3 levels were quantified and normalized to corresponding β-actin levels, which were presented as fold changes relative to controls that were set to 1. **p < 0.01, ***p < 0.001