Dataset Information

A mechanism of ubiquitin-independent proteasomal degradation of the tumor suppressors p53 and p73.

ABSTRACT: Protein degradation is an essential and highly regulated process. The proteasomal degradation of the tumor suppressors p53 and p73 is regulated by both polyubiquitination and by an ubiquitin-independent process. Here, we show that this ubiquitin-independent process is mediated by the 20S proteasomes and is regulated by NQO1. NQO1 physically interacts with p53 and p73 in an NADH-dependent manner and protects them from 20S proteasomal degradation. Remarkably, the vast majority of NQO1 in cells is found in physical association with the 20S proteasomes, suggesting that NQO1 functions as a gatekeeper of the 20S proteasomes. We further show that this pathway plays a role in p53 accumulation in response to ionizing radiation. Our findings provide the first evidence for in vivo degradation of p53 and p73 by the 20S proteasomes and its regulation by NQO1 and NADH level.

SUBMITTER: Asher G

PROVIDER: S-EPMC546509 | biostudies-other | 2005 Feb

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:The tumor suppressors p53, p73, and p63 are known to function as transcription factors. They promote either growth arrest or apoptosis, depending upon the DNA damage. A number of microRNAs (miRNAs) have been shown to function as transcriptional targets of p53 and they appear to aid p53 in promoting growth arrest and apoptosis. However, the question of p53/p63/p73 regulating the miRNA processing complex has not been addressed in depth so far. Comparative/computational genomic analysis was performed using Target scan, Mami, and Diana software to identify miRNAs that regulate the miRNA processing complex. Here, I present evidence for the first time that the tumor suppressors p53, p63, and p73 function as both positive and negative regulators of the miRNA processing components. Curated p53-dependent miRNA expression data was used to identify p53-miRs that target the components of the miRNA-processing complex. This analysis suggests that most of the components (mRNAs' 3'UTR) of the miRNA processing complex are targeted by p53-miRs. Remarkably, this data revealed the conserved nature of p53-miRs in targeting a number of components of the miRNA processing complex. p53/p73/p63 appears to regulate the major components of the miRNA processing, such as Drosha-DGCR8, Dicer-TRBP2, and Argonaute proteins. In particular, p53/p73/p63 appears to regulate the processing of miRNAs, such as let-7, miR-200c, miR-143, miR-107, miR-16, miR-145, miR-134, miR-449a, miR-503, and miR-21. Interestingly, there seems to be a phenotypic similarity between p63(-/-) and dicer(-/-) mice, suggesting that p63 and dicer could regulate each other. In addition, p63, p73, and the DGCR8 proteins contain a conserved interaction domain. Further, promoters of a number of components of the miRNA processing machinery, including dicer and P2P-R, contain p53-REs, suggesting that they could be direct transcriptional targets of p63/p73/p53. Together, this study provides mechanistic insights into how p53, p63, and p73 regulate the components of the miRNA processing; and how p53, TA-p63, and TA-p73 regulated miRNAs inhibit tumorigenesis, EMT, metastasis, and cancer stem cell proliferation.

Project description:The p53 family of proteins regulates the expression of target genes that promote cell cycle arrest and apoptosis, which may be linked to cellular growth control as well as tumor suppression. Within the p53 family, p53 and the transactivating p73 isoform (TA-p73) have hepatic-specific functions in development and tumor suppression. Here, we determined TA-p73 interactions with chromatin in the adult mouse liver and found forkhead box O3 (Foxo3) to be one of 158 gene targets. Global profiling of hepatic gene expression in the regenerating liver versus the quiescent liver revealed specific, functional categories of genes regulated over the time of regeneration. Foxo3 is the most responsive gene among transcription factors with altered expression during regenerative cellular proliferation. p53 and TA-p73 bind a Foxo3 p53 response element (p53RE) and maintain active expression in the quiescent liver. During regeneration of the liver, the binding of p53 and TA-p73, the recruitment of acetyltransferase p300, and the active chromatin structure of Foxo3 are disrupted along with a loss of Foxo3 expression. In agreement with the loss of Foxo3 transcriptional activation, a decrease in histone activation marks (dimethylated histone H3 at lysine 4, acetylated histone H3 at lysine 14, and acetylated H4) at the Foxo3 p53RE was detected after partial hepatectomy in mice. These parameters of Foxo3 regulation are reestablished with the completion of liver growth and regeneration and support a temporary suspension of p53 and TA-p73 regulatory functions in normal cells during tissue regeneration. p53-dependent and TA-p73-dependent activation of Foxo3 was also observed in mouse embryonic fibroblasts and in mouse hepatoma cells overexpressing p53, TA-p73alpha, and TA-p73beta isoforms.p53 and p73 directly bind and activate the expression of the Foxo3 gene in the adult mouse liver and murine cell lines. p53, TA-p73, and p300 binding and Foxo3 expression decrease during liver regeneration, and this suggests a critical growth control mechanism mediated by these transcription factors in vivo.

Dataset Information

A mechanism of ubiquitin-independent proteasomal degradation of the tumor suppressors p53 and p73.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets