Maximal serum stimulation of the c-fos serum response element requires both the serum response factor and a novel binding factor, SRE-binding protein.

We have previously reported on the presence of a CArG motif at -100 in the Rous sarcoma virus long terminal repeat which binds an avian nuclear protein termed enhancer factor III (EFIII) (A. Boulden and L. Sealy, Virology 174:204-216, 1990).

Physicochemical studies of human O6-methylguanine-DNA methyltransferase.

O6-Methylguanine-DNA methyltransferase, present in most organisms, removes mutagenic and carcinogenic O6-alkylguanine from DNA by accepting the alkyl group in a stoichiometric reaction. The protein has been partially purified from human placenta. It reacts with second-order rate constants of 2.

Identification of a third protein factor which binds to the Rous sarcoma virus LTR enhancer: possible homology with the serum response factor.

We have identified a new protein factor (EFIII) in nuclear extracts of quail fibroblasts and chick embryos which binds specifically in vitro to a 26-bp region of the Rous sarcoma virus (RSV) long terminal repeat (LTR) enhancer. The EFIII binding site in the RSV LTR exhibits a strong sequence homology to the serum response element (SRE). The SRE is a 22-bp cis-acting DNA sequence element, first identified upstream of the human c-fos gene, which can confer serum inducibility to heterologous promotors.

Effect of polyvalent metal ions on the reactivity of human O6-methylguanine-DNA methyltransferase.

Polyvalent metal ions are highly effective in inhibiting human O6-methylguanine-DNA methyltransferase, the repair protein responsible for the removal of the promutagenic and presumably procarcinogenic adduct, O6-alkylguanine, in DNA. The sulfhydryl group-reacting metal ions (Cd2+, Zn2+, Hg2+, Pb2+) completely inhibited the reaction at concentrations of 100-500 microM while other metal ions (Al3+, Fe3+) required concentrations of 1 mM or greater for significant reduction of the reaction rate. Inhibition by the former group of metals could be reversed by dithiothreitol but not by EDTA, while the opposite was true for the second group.