A platform for interrogating cancer-associated p53 alleles

Abstract

p53 is the most frequently mutated gene in human cancer. Compelling evidence argues that full transformation involves loss of growth suppression encoded by wild-type p53 together with poorly understood oncogenic activity encoded by missense mutations. Furthermore, distinguishing disease alleles from natural polymorphisms is an important clinical challenge. To interrogate the genetic activity of human p53 variants, we leveraged the Drosophila model as an in vivo platform. We engineered strains that replace the fly p53 gene with human alleles, producing a collection of stocks that are, in effect, ‘humanized’ for p53 variants. Like the fly counterpart, human p53 transcriptionally activated a biosensor and induced apoptosis after DNA damage. However, all humanized strains representing common alleles found in cancer patients failed to complement in these assays. Surprisingly, stimulus-dependent activation of hp53 occurred without stabilization, demonstrating that these two processes can be uncoupled. Like its fly counterpart, hp53 formed prominent nuclear foci in germline cells but cancer-associated p53 variants did not. Moreover, these same mutant alleles disrupted hp53 foci and inhibited biosensor activity, suggesting that these properties are functionally linked. Together these findings establish a functional platform for interrogating human p53 alleles and suggest that simple phenotypes could be used to stratify disease variants.

L3MBTL1 regulates ALS/FTD-associated proteotoxicity and quality control

“…4b), suggestive of impaired clearance. To test whether dp53, the Drosophila homolog of human p53 28, 29 , also affects SOD1 proteotoxicity, we crossed a stable dp53 RNAi strain to the mutant SOD1 flies, and observed that the reduction of dp53 significantly worsened the climbing deficits as well as increased the accumulation of mutant SOD1 protein (Fig. 4a,b), consistent with the role of p53 as a positive regulator of protein quality control.…”

Molecular Basis of Tumor Heterogeneity in Endometrial Carcinosarcoma

“…Most of the mutations are located in the DNA binding domain, and very few are present in the translocation and tetramerization motifs. In the DNA binding domain, 32% of mutations are located on known hotspot residues, and the most frequent are the R248Q and R273C/H (12% and 7%, respectively) followed by H179R/D, H193R/Y, and S241Y (5% each), () [41].…”

p53 in the game of transposons

“…Like mammalian counterparts, p53 genes in flies and worms act to specify adaptive responses to damage and promote genome stability (reviewed in ). As transcription factors, fly p53 and human p53 bind to identical sequence elements , but perhaps the most definitive evidence for functional conservation comes from studies on “humanized p53 fly strains,” where human p53 genes were used to rescue defective phenotypes caused by mutations in the fly counterpart . Upstream regulators in these networks are also conserved.…”