Examining the Effect of the E227Q Mutation on CDX2 in Transcription and ATM Inhibition

Ian Chiu, Dr. Soo Hyun Yang, Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712

Ataxia-telangiectasia (AT) is a rare, neurodegenerative disease characterized by a predisposition to cancer, immunodeficiency, and neuropathy. The cause of AT is linked to one or more mutations in the Ataxia-telangiectasia mutated (ATM) gene. Its gene product, ATM protein kinase, acts as a signaling molecule in many different cell pathways such as double-strand break (DSB) repairs. In the presence of DSBs, ATM is activated via its interaction with the Mre11-Rad50-Nbs1 (MRN) complex, and this interaction was shown to phosphorylate downstream proteins necessary for cell cycle checkpoint regulation, DSB repair, and apoptosis. Although the interaction between ATM-MRN is crucial for signaling DSB repair, how this interaction is mediated within cells remains unclear. The Caudal Type Homeobox Transcription Factor 2 (CDX2) belongs to the homeobox gene family that is specifically expressed in intestinal epithelial cells. Recently, studies have shown that CDX2 disrupts ATM-MRN interaction via its homeobox domain, which is also the region responsible for transcription. The objective of this study is to identify a separate function mutant of CDX2 separating its role in ATM-MRN inhibition and transcription activation. To conduct this study, a point mutation was introduced into the CDX2 homeobox domain via site-directed mutagenesis. This mutation was introduced within the homeobox domain, but away from the DNA binding-site, suggesting that the mutation will have minimal effect on the transcriptional activity. To assess the DNA binding affinity of the mutant CDX2, EMSA will be performed. Two-step RT-PCR assays will be performed using human cell expression vectors to assess the CDX2 mutant transcription activities. After confirming the wild-type transcription activity of CDX2 mutants, in vitro ATM kinase assays will be run to assess CDX2 mutant effect on ATM inhibition. Ultimately, this project will provide a deeper understanding of the regulatory mechanism CDX2 possesses on ATM signaling functions in human epithelial cells. 

Additional Abstract Information

Presenter: Ian Chiu

Institution: University of Texas at Austin

Type: Poster

Subject: Biochemistry

Status: Approved

Time and Location

Session: Poster 1
Date/Time: Mon 1:30pm-2:30pm
Session Number: 2133