Masaharu Sakai

A novel octamer binding transcription factor is differentially expressed in mouse embryonic cells

We have identified a novel octamer binding factor (Oct-3) in P19 embryonal carcinoma cells. Oct-3, which recognizes the typical octamer motif (ATTTGCAT) as well as the AT-rich sequence TTAAAATTCA, is present in P19 stem cells but disappears when the cells are induced to differentiate by retinoic acid (RA). Cloned cDNA corresponding to Oct-3 encodes a protein of 377 amino acids. Oct-3 has a conserved POU domain, but the remaining part is distinct from other POU domain-containing proteins such as Oct-1 and Oct-2. mRNA of 1.5 kb coding for Oct-3 is abundant in P19 stem cells but is dramatically repressed during RA-induced differentiation. Repression of the 1.5 kb mRNA is rapid and specific to RA. In mouse, oct-3 mRNA is undetectable in all the adult organs examined. The N-terminal proline-rich region of Oct-3, when fused to the DNA binding domain of c-Jun, functions as a transcriptional activating domain. We suggest that Oct-3 is a novel octamer binding transcription factor that is developmentally regulated during mouse embryogenesis.

LEVELS OF GLUTATHIONES TRANSFERASE π mRNA IN HUMAN LUNG CANCER CELL LINES CORRELATE WITH THE RESISTANCE TO CISPLATIN AND CARBOPLATIN

The amounts of mRNA for glutathione S transferase π (GST π) were significantly lower in 3 human small cell lung cancer (SCLC) cell lines than in 3 non small cell lung cancer (NSCLC) cell lines. The sensitivities of the 3 SCLC cell lines to cisplatin and carboplatin were much higher than those of the 3 NSCLC cell lines. These results indicate that low levels of GST π mRNA expression in SCLC cell lines inversely correlate to high sensitivity to cisplatin and carboplatin, and further suggest that GST π may play an important role in intracellular inactivation of these drugs.