Oh-Sung Park

Hypothyroidism induced by polychlorinated biphenyls and up-regulation of transthyretin.

Polychlorinated biphenyls are environmental pollutants that are toxic to many biological systems. This study examined whether or not PCB126 and PCB114 have adverse effects on the serum thyroxine level and the serum proteome in rats. The results showed a lower serum total thyroxine level in the PCB126 and PCB114-treated groups than the control. Western blotting showed that the levels of transthyretin expression were significantly higher in the PCB-treated group than the control group. These results suggest that the PCB-mediated hypothyroidism is caused by the displacement of thyroxine from transthyretin.

Identification of trophoblast-specific binding sites for GATA-2 that are essential for rat placental lactogen-I gene expression

We identified a 3.4-kb 5′-flanking region of the rPL-I gene and examined its promoter activity using rat trophoblast Rcho-1 cells. A regulatory element between base pairs (bp) −2,487 and −2,310 in the 5′-flanking region was essential for maximum promoter activity of the rPL-I gene. This regulatory element was further characterized between bp −2,443 to −2,415 and −2,374 to −2,345. Electrophoretic mobility shift analysis showed that the interaction of nuclear extract proteins from differentiated Rcho-1 cells was inhibited by competition with a GATA-like sequence in the promoter, but not by a mutated GATA sequence. Moreover, the promoter activity of 2487 eLuc containing two novel GATA sites was significantly elevated by co-transfection of a GATA-2 expression vector in proliferating Rcho-1 cells. Our results demonstrate that GATA-2 is involved in multiple promoter regions to activate the specific expression of the rPL-I gene in placental tissue.