Fig. 6

PRRG4 enhances POLG transcription via STAT3. A The consensus STAT3 DNA binding motif was downloaded from JASPAR. B Different pGL3-POLG promoter (up to − 1516 bp)-luciferase reporter (luc) constructs. Two predicted STAT3 binding sites, site1 and site2 in POLG promoter are indicated by arrowhead. Mut1 and Mut2 are corresponding site1 and site2 that were mutated respectively in positions indicated by red letters. C Luciferase reporter assay shows that predicted STAT3 binding site1 mediates PRRG4 enhancement of POLG promoter activity. The indicated luciferase reporter plasmids together with pRL-TK normalizing plasmid were transiently transfected into MDA-MB-231 cells with vector and PRRG4-WT. Forty-eight hours later, cells were subjected to dual-luciferase activity assay. D PRRG4 enhances POLG promoter activity depending on STAT3. The indicated luciferase reporter plasmids together with pRL-TK normalizing plasmid were transiently cotransfected into MDA-MB-231 cells with vector alone or PRRG4-WT. Twenty-eight hours later, MDA-MB-231 cells were treated with vehicle or Stattic (3 µM) for 20 h. E Expression of STAT3-DN decreases POLG promoter activity in SUM149PT cells. SUM149PT cells with vector alone and STAT3-DN were transiently cotransfected with the indicated luciferase reporter plasmids together with pRL-TK normalizing plasmid. *p < 0.05, **p < 0.01, ***p < 0.001, ns: no significance