Dataset Information

P53-Related Transcription Targets of TAp73 in Cancer Cells-Bona Fide or Distorted Reality?

ABSTRACT: Identification of p73 as a structural homolog of p53 fueled early studies aimed at determining if it was capable of performing p53-like functions. This led to a conundrum as p73 was discovered to be hardly mutated in cancers, and yet, TAp73, the full-length form, was found capable of performing p53-like functions, including transactivation of many p53 target genes in cancer cell lines. Generation of mice lacking p73/TAp73 revealed a plethora of developmental defects, with very limited spontaneous tumors arising only at a later stage. Concurrently, novel TAp73 target genes involved in cellular growth promotion that are not regulated by p53 were identified, mooting the possibility that TAp73 may have diametrically opposite functions to p53 in tumorigenesis. We have therefore comprehensively evaluated the TAp73 target genes identified and validated in human cancer cell lines, to examine their contextual relevance. Data from focused studies aimed at appraising if p53 targets are also regulated by TAp73-often by TAp73 overexpression in cell lines with non-functional p53-were affirmative. However, genome-wide and phenotype-based studies led to the identification of TAp73-regulated genes involved in cellular survival and thus, tumor promotion. Our analyses therefore suggest that TAp73 may not necessarily be p53's natural substitute in enforcing tumor suppression. It has likely evolved to perform unique functions in regulating developmental processes and promoting cellular growth through entirely different sets of target genes that are not common to, and cannot be substituted by p53. The p53-related targets initially reported to be regulated by TAp73 may therefore represent an experimental possibility rather than the reality.

SUBMITTER: Wang C

PROVIDER: S-EPMC7072922 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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p53-Related Transcription Targets of TAp73 in Cancer Cells-Bona Fide or Distorted Reality?

Wang Chao C Teo Cui Rong CR Sabapathy Kanaga K

International journal of molecular sciences 20200217 4

Identification of p73 as a structural homolog of p53 fueled early studies aimed at determining if it was capable of performing p53-like functions. This led to a conundrum as <i>p73</i> was discovered to be hardly mutated in cancers, and yet, TAp73, the full-length form, was found capable of performing p53-like functions, including transactivation of many p53 target genes in cancer cell lines. Generation of mice lacking p73/TAp73 revealed a plethora of developmental defects, with very limited spo ...[more]

PMID: 32079264

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Project description:Mammalian prions are PrP proteins with altered structures causing transmissible fatal neurodegenerative diseases. They are self-perpetuating through formation of beta-sheet-rich assemblies that seed conformational change of cellular PrP. Pathological PrP usually forms an insoluble protease-resistant core exhibiting beta-sheet structures but no more alpha-helical content, loosing the three alpha-helices contained in the correctly folded PrP. The lack of a high-resolution prion structure makes it difficult to understand the dynamics of conversion and to identify elements of the protein involved in this process. To determine whether completeness of residues within the protease-resistant domain is required for prions, we performed serial deletions in the helix H2 C terminus of ovine PrP, since this region has previously shown some tolerance to sequence changes without preventing prion replication. Deletions of either four or five residues essentially preserved the overall PrP structure and mutant PrP expressed in RK13 cells were efficiently converted into bona fide prions upon challenge by three different prion strains. Remarkably, deletions in PrP facilitated the replication of two strains that otherwise do not replicate in this cellular context. Prions with internal deletion were self-propagating and de novo infectious for naive homologous and wild-type PrP-expressing cells. Moreover, they caused transmissible spongiform encephalopathies in mice, with similar biochemical signatures and neuropathologies other than the original strains. Prion convertibility and transfer of strain-specific information are thus preserved despite shortening of an alpha-helix in PrP and removal of residues within prions. These findings provide new insights into sequence/structure/infectivity relationship for prions.Prions are misfolded PrP proteins that convert the normal protein into a replicate of their own abnormal form. They are responsible for invariably fatal neurodegenerative disorders. Other aggregation-prone proteins appear to have a prion-like mode of expansion in brains, such as in Alzheimer's or Parkinson's diseases. To date, the resolution of prion structure remains elusive. Thus, to genetically define the landscape of regions critical for prion conversion, we tested the effect of short deletions. We found that, surprisingly, removal of a portion of PrP, the C terminus of alpha-helix H2, did not hamper prion formation but generated infectious agents with an internal deletion that showed characteristics essentially similar to those of original infecting strains. Thus, we demonstrate that completeness of the residues inside prions is not necessary for maintaining infectivity and the main strain-specific information, while reporting one of the few if not the only bona fide prions with an internal deletion.

Dataset Information

P53-Related Transcription Targets of TAp73 in Cancer Cells-Bona Fide or Distorted Reality?

Publications

p53-Related Transcription Targets of TAp73 in Cancer Cells-Bona Fide or Distorted Reality?

Similar Datasets

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