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Interactions between c‐Myc/AP2 α regulate cell growth and survival
Author(s) -
Yu Lei,
Domann Frederick
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a70
Subject(s) - electrophoretic mobility shift assay , microbiology and biotechnology , transcription factor , cell growth , biology , recombinant dna , cell culture , dna binding protein , hacat , dna , binding protein , carcinogenesis , plasma protein binding , chemistry , biochemistry , gene , genetics
c‐Myc and AP2α are both important transcription factors that are involved in cell proliferation, differentiation, carcinogenesis and apoptosis. c‐Myc binds to a central CAC(G/A)TG sequence while AP2α binds to GCCN3‐5GGC. It has been shown that AP2α can inhibit c‐Myc DNA binding activity through either competing for the DNA binding site, or through protein/protein interactions. Since the interaction sites are the DNA binding domains of both proteins, we hypothesized conversely that c‐Myc would block AP2α DNA binding activity. DNA binding activity of recombinant AP2α protein was determined by electrophoresis mobility shift assay (EMSA) in the presence and absence of recombinant c‐Myc protein. Our EMSA showed that c‐Myc blocked AP2α DNA binding activity stoichiometrically. However, if DNA probe was incubated with AP2α protein prior to adding c‐Myc protein, such inhibitory effect was greatly alleviated. In addition to wild type AP2, a C‐terminal truncated AP2 protein, AP2 S420X was also tested, and displayed similar behavior. Studies to examine the effect of the c‐Myc:AP2α interaction in vivo were conducted in two cell lines: HaCaT cells, which have abundant active AP2α, and MB‐MDA‐231 cells, which does not express AP2α. Both cell lines were infected with adenoviral expression constructs as follows: control, AP2α, c‐Myc and AP2α+c‐Myc, respectively. The clonogenic survival rate was found to be significantly lower in cells infected with c‐Myc versus control or AP2α only group. Conversely, coinfection with AP2α+c‐Myc was able to double cell survival and increase growth rate compared to cells infected with c‐Myc alone. We conclude that c‐Myc is an inhibitor of AP2α DNA binding, and AP2α counteracts the cytotoxic effect of c‐Myc. Supported by NIH CA 66081