The tumor suppressor p53 plays a prominent role in cancer and much of human biology. Many functions have been attributed to p53, including roles in repair and recombination, association with proteins involved in genome stability, and chromatin modification. However, its broadest cellular effect is that of a transcription factor (TF. As a TF, p53 is regulated through multiple post translational modifications by a variety of cellula stresses including DNA damage. Our laboratory recently uncovered that TAF1 phosphorylates p53 at Thr55 on the p21 promoter and this phosphorylation leads to dissociation of p53 from the promoter and termination of p21 transcription after DNA damage. TAF1 is the largest subunit of transcription factor TFIID and a cell cycle regulatory protein important for progression through the G1 phase. Interestingly, we also uncovered that TAF1 phosphorylates p53 in a cellular ATP level-dependent manner. Because high glucose conditions (HG) can potentially increase cellular ATP levels, we hypothesize that it may enhance Thr55 phosphorylation, leading to inactivation of the protein upon DNA damage. To test this hypothesis, we show indeed that p21 transcription is reduced upon DNA damage under HG conditions. Our findings raised fundamental questions as to what extent HG contributes to inhibition of p53 activation genome wide in response to DNA damage. This research will thus focus on identifying and exploring the genome wide effect of HG on p53-target genes regulated by DNA damage and exploring the molecular pathway through which this regulation occurs. Our long term goal is to establish a molecular mechanism by which hyperglycemia, commonly found in diabetics, can indirectly contribute towards malignant transformation. We propose to carry out this research project through the following three aims: (1) Identify p53 target genes that are affected by HG in response to DNA damage genome wide by RNA-sequencing. (2) Globally identify p53 bound promoters that are affected by HG in response to DNA damage by ChIP-sequencing. (3) Test the generality of ATP-dependent TAF1 phosphorylation as a mechanism for inhibition of p53 activity.
The relationship between diabetes and the development of cancer remains unknown. The proposed project will explore the effect of high glucose on inhibition of the tumor suppressor p53. This project has great potential to provide molecular insight into how cellular metabolites affect tumor suppressor function and thus is highly relevant to human health.
|Wu, Yong; Lin, Joy C; Piluso, Landon G et al. (2014) Phosphorylation of p53 by TAF1 inactivates p53-dependent transcription in the DNA damage response. Mol Cell 53:63-74|