Lotz Rebecca, Osterburg Christian, Chaikuad Apirat, Weber Sabrina, Akutsu Masato, Machel Anne Christin, Beyer Ulrike, Gebel Jakob, Löhr Frank, Knapp Stefan, Dobbelstein Matthias, Lu Xin, Dötsch Volker
Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, 60438, Frankfurt, Germany.
Institute of Pharmaceutical Chemistry, Goethe University, 60438, Frankfurt, Germany.
Cell Death Dis. 2025 Jan 6;16(1):4. doi: 10.1038/s41419-024-07320-2.
The transcription factor p63 is expressed in many different isoforms as a result of differential promoter use and splicing. Some of these isoforms have very specific physiological functions in the development and maintenance of epithelial tissues and surveillance of genetic integrity in oocytes. The ASPP family of proteins is involved in modulating the transcriptional activity of the p53 protein family members, including p63. In particular, iASPP plays an important role in the development and differentiation of epithelial tissues. Here we characterize the interaction of iASPP with p63 and show that it binds to the linker region between the DNA binding domain and the oligomerization domain. We further demonstrate that this binding site is removed in a splice variant of p63 where a stretch of five amino acids is replaced with a single alanine residue. This stretch contains a degenerate class II SH3 domain binding motif that is responsible for interaction with iASPP, as well as two positively charged amino acids. Moreover, the concomitant loss of the charged amino acids in the alternatively spliced version decreases the affinity of p63 to its cognate DNA element two- to threefold. mRNAs encoding full-length p63, as well as its alternatively spliced version, are present in all tissues that we investigated, albeit in differing ratios. We speculate that, through the formation of hetero-complexes of both isoforms, the affinity to DNA, as well as the interaction with iASPP, can be fine-tuned in a tissue-specific manner.
转录因子p63由于启动子使用和剪接的差异而以多种不同的异构体形式表达。其中一些异构体在上皮组织的发育和维持以及卵母细胞遗传完整性监测中具有非常特定的生理功能。ASPP蛋白家族参与调节p53蛋白家族成员（包括p63）的转录活性。特别是，iASPP在上皮组织的发育和分化中起重要作用。在这里，我们描述了iASPP与p63的相互作用，并表明它与DNA结合结构域和寡聚化结构域之间的连接区结合。我们进一步证明，在p63的一个剪接变体中，这段由五个氨基酸组成的序列被单个丙氨酸残基取代，该结合位点被去除。这段序列包含一个负责与iASPP相互作用的简并II类SH3结构域结合基序，以及两个带正电荷的氨基酸。此外，剪接变体中带电荷氨基酸的同时缺失使p63与其同源DNA元件的亲和力降低了两到三倍。编码全长p63及其剪接变体的mRNA存在于我们研究的所有组织中，尽管比例不同。我们推测，通过两种异构体形成异源复合物，可以以组织特异性方式对DNA亲和力以及与iASPP的相互作用进行微调。
