Figure 7: HCMV infection abrogates TRIM31 expression.

(a) Left, HT-29 cells were infected with invasive Shigella M90T strain. TRIM31 mRNA levels were determined by RT-PCR. Right, Quantification of TRIM31 mRNA levels normalized against GAPDH, which was used as a loading control. *P<0.01 (Student’s t-test). (b) HT-29 cells were treated with LPS (100 ng ml⁻¹) for 0, 1 or 3 h, and then TRIM31 mRNA was measured by RT-PCR. Right, Quantification of TRIM31 mRNA levels normalized against GAPDH, which was used as a loading control. *P<0.01 (Student’s t-test). (c) TRIM31 mRNA was measured by RT-PCR in HeLa cells treated with LPS (100 ng ml⁻¹) for 0, 1 or 3 h. *P<0.01 (Student’s t-test). (d) Cell death was assessed by propidium iodide (PI) staining of mock or TRIM31-Myc-expressing HeLa cells infected with M90T-GFP followed by flow cytometric analysis. Values represent the average of three independent experiments. *P<0.05 (Student’s t-test). (e) HCMV infection down-regulates TRIM31 expression. Wild-type HCMV AD169 strain was infected into the intestinal epithelial cell line, Caco-2, for 48 h, and then HCMV immediate early gene (IE1), LC3, or TRIM31 mRNA was measured by RT-PCR. (f) Quantification of TRIM31 and LC3 mRNA levels normalized against GAPDH. *P<0.01 (Student’s t-test). (g) HCMV-infected intestinal cells show a considerable increase in bacteria load. Intestinal cells were infected with HCMV for 48 h, followed by infection with Shigella prior to measuring the degree of bacterial growth. TRIM31 or IE1 mRNA levels were determined by RT-PCR. Values represent the average number of colonies from three independent experiments. *P<0.01 (Student’s t-test). All data are representative of at least three independent experiments (mean±s.d. in a–d, f–g). (h) Proposed model of TRIM31-mediated alternative autophagy process in the intestinal epithelial cells.