Heterogeneity of ternary complex factors in HeLa cell nuclear extracts

Ternary complex factors (TCFs) interact with the serum response factor and DNA containing the c-fos serum response element to form a ternary complex that mediates induction of c-fos. TCF activities were partially purified from HeLa cell nuclear extracts by DNA-cellulose and anion-exchange chromatography followed by two-dimensional gel electrophoresis. Four different protein spots (p60TCF, p62TCF, p62.5TCF, and p64TCF) show renaturable TCF activity. One, p62TCF, was indistinguishable from the Ets protein Elk-1 in gel shift analyses, while none of the HeLa TCFs resembled the other cloned TCFs, SAP-1a and SAP-1b. In two-dimensional gel analysis, Elk-1, SAP-1a, and SAP-1b displayed different pI and M(r) values and in vitro synthesized Elk-1 comigrated with the p62TCF spot. Both reacted with Elk-1 specific antisera, as did the major proportion of TCF activity present in HeLa crude extracts. We conclude that p62TCF is composed of Elk-1, whereas the identities of the other identified TCFs (p60TCF, p62.5TCF, and p64TCF) are still unknown.