BCM 262 Introduction to Biological Chemistry Spring 2009

Oanh VuBCM 2622/16/15

This paper addresses the mechanism of the aggregation tendencies of p53. p53 is known for its pivotal role in cell cycle regulation. It act as a transcriptional regulator, which binds to DNA and thus suppresses cell cycle progression and induces apoptosis in response to DNA damages. However, various cancer mutant studies have suggested that p53 lost its function when it formed amyloid structures in vivo. Amyloidosis is an abnormal protein folding, which leads to protein dysfunction. Therefore, this study aimed to investigate how p53 aggregates into amyloid formation and identify which segments of p53 might be involved in this abnormal protein folding.The study combined computational and experimental approaches. The researchers used TANGO, an amyloid algorithm, to show that a conserved region, PILTIITL (P8) was most likely to form amyloids. To study the role of P8 in p53s abnormal conformation, the core domains of the p53 were overexpressed in E.coli and then the target protein was purified from bacterial extracts using Ni-high affinity chromatography. Various techniques such as circular dichroism spectroscopy, thioflvin T fluorescence, congo red binding, dot blot analysis and in-cell seeding and immunocytochemistry were also used to observe changes in the proteins secondary and tertiary structures. Wet lab results suggested that the sequence of P8 was mainly responsible for the abnormal conformation of p53. The authors showed that 8-residue fibrils induced aggregation of p53 core domain in vitro and full-length p53 in vivo. Using atom Molecular Dynamic simulations, they found that the P8 undergoes secondary structure transition from random coil-like structures to beta-rich aggregates. These discoveries can be utilized to help develop therapeutics against p53s loss of function.

Reference: Ghosh S., Ghosh D., Ranganathan S., Anoop A., Kumar S., Nath N., Padinhateeri R., and Maji S. Investigating the Intrinsic Aggregation Potential of Evolutionarily Conserved Segments in p53, Biochemistry, 2014, 53, 5995-6010."