Heat treatment-induced functional and structural aspects of Mus musculus TAp63γ

TAp63γ plays as an important tumor suppressor gene protecting from cancer development, especially in p53-deficient cancer cells under stresses. Here, we investigated the effects of heat treatment on the functional and structural stabilities of TAp63γ by means of the electrophoretic mobility shift assay, intrinsic tryptophan fluorescence, exogenous ANS fluorescence, and CD spectroscopies. The electrophoretic mobility shift assay result showed that the DNA binding activity of GST-TAp63γ decreased above 55 °C. The intrinsic fluorescence spectra indicated an increase of the hydrophobicity and a decrease of the polarity in the microenvironments around the tyrosine and tryptophan residues. The ANS fluorescence spectra suggested that the hydrophobic pockets in TAp63γ gradually unfolded below 50 °C. The above results indicated that TAp63γ partially unfolded at 55 °C, while the CD result showed that TAp63γ still processed a pronounced secondary structure at the same temperature, suggesting that heat treatment possibly induced the molten globule state of TAp63γ, which was an intermediate state between the native and denatured protein. Taken together, TAp63γ is a relatively unstable protein, but it has higher activity than p53 at about 50 °C. The presented work also implies that TAp63γ may play an important role in stressed microenvironments especially when p53 is deficient.