REGULATORY SEQUENCES REQUIRED FOR HST-1 EXPRESSION IN EMBRYONAL CARCINOMA-CELLS

The hst-1 gene, which is implicated in mammalian embryonic development and morphological transformation of NIH3T3 cells, is expressed in und ifferentiated F9 cells, but not in differentiated F9 and other well-di fferentiated cells, such as PYS-2, NIH3T3 and HeLa cells. An octamer e lement present in the 3' untranslated region acts as an enhancer. Alth ough Oct3 is down-regulated when F9 cells are differentiated, transien t expression of Oct3 did not enhance the hst-1 promoter activity in He La, NIH3T3 or PYS-2 cells. Thus, the role of Oct3 on hst-1 expression remains elusive, and an additional transcription factor which interact s may regulate hst-1 transcription in association with Oct1, Oct3 or b oth.