Transcriptional Regulation of Human NANOG by Alternate Promoters in Embryonic Stem CellsSatyabrata Das1, Snehalata Jena1, Eun-Mi Kim1, Nicholas Zavazava1 and Dana N. Levasseur1,2*
- Corresponding Author:
- Dana N. Levasseur
285 Newton Road
Department of Internal Medicine
Roy J. and Lucille A. Carver College of Medicine
Iowa City, IA, 52242 USA
E-mail: [email protected]
Received Date: July 18, 2012; Accepted Date: August 22, 2012; Published Date: August 24, 2012
Citation: Das S, Jena S, Kim EM, Zavazava N, Levasseur DN, et al. (2012) Transcriptional Regulation of Human NANOG by Alternate Promoters in Embryonic Stem Cells. J Stem Cell Res Ther S10:009. doi:10.4172/2157-7633.S10-009
Copyright: © 2012 Das S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Introduction: The potential of pluripotent stem cells to be used for cell therapy depends on a comprehensive understanding of the molecular mechanisms underlying their unique ability to specify cells of all germ layers while undergoing unlimited self-renewal. Alternative splicing and alternate promoter selection contribute to this mechanism by increasing the number of transcripts generated from a single gene locus and thus enabling expression of novel protein variants which may differ in their biological role. The homeodomain-containing transcription factor NANOG plays a critical role in maintaining the pluripotency of Embryonic Stem Cells (ESC). Therefore, a thorough understanding of the transcriptional regulation of the NANOG locus in ESCs is necessary.
Methods: Regulatory footprints and transcription levels were identified for NANOG in human embryonic stem cells from data obtained using high-throughput sequencing methodologies. Quantitative real-time PCR following reverse transcription of RNA extracted human ESCs was used to validate the expression of transcripts from a region that extends upstream of the annotated NANOG transcriptional start. Promoter identification and characterization was performed using promoter reporter and electrophoretic mobility shift assays.
Results: Transcriptionally active chromatin marking and transcription factor binding site enrichment were
observed at a region upstream of the known transcriptional start site in NANOG. Expression of novel transcripts from this transcriptionally active region confirmed the existence of NANOG alternative splicing in human ESCs. We identified an alternate NANOG promoter of significant strength at this upstream region. We also discovered that NANOG autoregulates its expression by binding to its proximal downstream promoter.
Conclusion: Our study reveals novel transcript expression from NANOG in human ESCs, indicating that
alternative splicing increases the diversity of transcripts originating from the NANOG locus and that these transcripts are expressed by an alternate promoter. Alternative splicing and alternate promoter usage collaborate to regulate NANOG, enabling its function in the maintenance of ESCs.