Abstract The hst-1 gene, which is implicated in mammalian embryonic development and morphological transformation of NIH3T3 cells, is expressed in undifferentiated F9 cells, but not in differentiated F9 and other well-differentiated cells, such as PYS-2, NIH3T3 and HeLa cells. An octamer element present in the 3' untranslated region acts as an enhancer. Although Oct3 is down-regulated when F9 cells are differentiated, transient expression of Oct3 did not enhance the hst-1 promoter activity in HeLa, NIH3T3 or PYS-2 cells. Thus, the role of Oct3 on hst-1 expression remains elusive, and an additional transcription factor which interacts may regulate hst-1 transcription in association with Oct1, Oct3 or both.

Abstract The activating combination of CD2 antibodies Leu-5b plus 9.1 stimulates tyrosine phosphorylation in the human T cell line Jurkat. The tyrosine phosphorylation has the same molecular weight pattern as that seen when cells are stimulated on the CD3 receptor with OKT3 antibodies. These data provide evidence that signal transduction by the CD2 receptor is coupled to an increase in tyrosine phosphorylation that is similar to that coupled to the CD3 receptor.