Identifier

etd-06272016-122920

Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Restricted Dissertation

Abstract

Paternally expressed gene 3 (Peg3) is an imprinted gene that encodes a protein with twelve C2H2 zinc finger domains. Thus, PEG3 protein is predicted to serve as a transcription factor that may regulate other gene expression. Chromatin immunoprecipitation (ChIP) experiment revealed a list of genes that are bound by PEG3, supporting PEG3 is a DNA-binding protein. Genome wide expression analysis using wild type and Peg3 knockout mouse models further suggested that a large number of genes were up-regulated in Peg3 knockout model, including imprinted genes and some tissue-specific genes, suggesting that PEG3 may mainly function as a repressor for its downstream genes. It is well known that most imprinted genes are organized into clusters (imprinted domains) to share cis-acting elements which can regulate imprinted gene expression. However, in Peg3 imprinted domain, one of my studies suggested that two oppositely imprinted genes in Peg3 imprinted domain could interact through their gene products rather than shared cis regulatory elements. According to the results, paternally expressed Peg3 controls maternally expressed Zim1 as a trans factor. Removing PEG3 resulted in elevated expression of Zim1, thus PEG3 should serve as a repressor for Zim1. ChIP experiment further suggested that PEG3 might repress Zim1 expression through SETDB1/KAP1-driven H3K9me3 mechanism. Subsequent ChIP-seq analysis using mouse embryonic fibroblast (MEF) cells further identified 16 target genes as PEG3 downstream genes. Interestingly, most of these genes showed high level of expression in oocyte, in which Peg3 is not expressed. Furthermore, qRT-PCR analysis confirmed that PEG3 mainly functions as a repressor for these downstream genes. In addition, electromobility shift assay (EMSA) and the luciferase reporter assay further demonstrated that PEG3 can directly bind to H19-ICR to repress H19 expression. Overall, the research presented in this dissertation advances our understanding of the repression function of PEG3 protein and its potential tumor suppressor function linked to its downstream genes.

Date

2016

Document Availability at the Time of Submission

Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.

Committee Chair

Kim, Joomyeong

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