TY - JOUR
T1 - Mapping of ESE-1 subdomains required to initiate mammary epithelial cell transformation via a cytoplasmic mechanism
AU - Prescott, Jason D.
AU - Poczobutt, Joanna M.
AU - Tentler, John J.
AU - Walker, Darius M.
AU - Gutierrez-Hartmann, Arthur
N1 - Funding Information:
We thank Dr. Heide Ford for critical review of this manuscript, Dr. Melissa Gonzales for providing the pEGFP-ESE-1ΔDBD plasmid, and Tammy Trudeau for help with isolation of mAB405 antibody. DNA sequencing was provided by Core Facility of the University of Colorado Cancer Center (NIH P30 CA 46934). Fluorescence microscopy equipment was provided by the University of Colorado Denver Light Microscopy Facility. Monoclonal antibody production was conducted in collaboration with Protein Production-Moab-Tissue Culture Core of the University of Colorado Cancer Center. This work was supported by DOD DAMD 17-00-1-0474 grant to JDP, NIH T32DK007446-28 support for JMP and by DOD DAMD 17-00-1-0476 grant to AGH.
PY - 2011/8/28
Y1 - 2011/8/28
N2 - Background: The ETS family transcription factor ESE-1 is often overexpressed in human breast cancer. ESE-1 initiates transformation of MCF-12A cells via a non-transcriptional, cytoplasmic process that is mediated by a unique 40-amino acid serine and aspartic acid rich (SAR) subdomain, whereas, ESE-1's nuclear transcriptional property is required to maintain the transformed phenotype of MCF7, ZR-75-1 and T47D breast cancer cells.Results: To map the minimal functional nuclear localization (NLS) and nuclear export (NES) signals, we fused in-frame putative NLS and NES motifs between GFP and the SAR domain. Using these GFP constructs as reporters of subcellular localization, we mapped a single NLS to six basic amino acids (242HGKRRR247) in the AT-hook and two CRM1-dependent NES motifs, one to the pointed domain (NES1: 102LCNCALEELRL112) and another to the DNA binding domain (DBD), (NES2: 275LWEFIRDILI284). Moreover, analysis of a putative NLS located in the DBD (316GQKKKNSN323) by a similar GFP-SAR reporter or by internal deletion of the DBD, revealed this sequence to lack NLS activity. To assess the role of NES2 in regulating ESE-1 subcellular localization and subsequent transformation potency, we site-specifically mutagenized NES2, within full-length GFP-ESE-1 and GFP-NES2-SAR reporter constructs. These studies show that site-specific mutation of NES2 completely abrogates ESE-1 transforming activity. Furthermore, we show that exclusive cytoplasmic targeting of the SAR domain is sufficient to initiate transformation, and we report that an intact SAR domain is required, since block mutagenesis reveals that an intact SAR domain is necessary to maintain its full transforming potency. Finally, using a monoclonal antibody targeting the SAR domain, we demonstrate that the SAR domain contains a region accessible for protein - protein interactions.Conclusions: These data highlight that ESE-1 contains NLS and NES signals that play a critical role in regulating its subcellular localization and function, and that an intact SAR domain mediates MEC transformation exclusively in the cytoplasm, via a novel nontranscriptional mechanism, whereby the SAR motif is accessible for ligand and/or protein interactions. These findings are significant, since they provide novel molecular insights into the functions of ETS transcription factors in mammary cell transformation.
AB - Background: The ETS family transcription factor ESE-1 is often overexpressed in human breast cancer. ESE-1 initiates transformation of MCF-12A cells via a non-transcriptional, cytoplasmic process that is mediated by a unique 40-amino acid serine and aspartic acid rich (SAR) subdomain, whereas, ESE-1's nuclear transcriptional property is required to maintain the transformed phenotype of MCF7, ZR-75-1 and T47D breast cancer cells.Results: To map the minimal functional nuclear localization (NLS) and nuclear export (NES) signals, we fused in-frame putative NLS and NES motifs between GFP and the SAR domain. Using these GFP constructs as reporters of subcellular localization, we mapped a single NLS to six basic amino acids (242HGKRRR247) in the AT-hook and two CRM1-dependent NES motifs, one to the pointed domain (NES1: 102LCNCALEELRL112) and another to the DNA binding domain (DBD), (NES2: 275LWEFIRDILI284). Moreover, analysis of a putative NLS located in the DBD (316GQKKKNSN323) by a similar GFP-SAR reporter or by internal deletion of the DBD, revealed this sequence to lack NLS activity. To assess the role of NES2 in regulating ESE-1 subcellular localization and subsequent transformation potency, we site-specifically mutagenized NES2, within full-length GFP-ESE-1 and GFP-NES2-SAR reporter constructs. These studies show that site-specific mutation of NES2 completely abrogates ESE-1 transforming activity. Furthermore, we show that exclusive cytoplasmic targeting of the SAR domain is sufficient to initiate transformation, and we report that an intact SAR domain is required, since block mutagenesis reveals that an intact SAR domain is necessary to maintain its full transforming potency. Finally, using a monoclonal antibody targeting the SAR domain, we demonstrate that the SAR domain contains a region accessible for protein - protein interactions.Conclusions: These data highlight that ESE-1 contains NLS and NES signals that play a critical role in regulating its subcellular localization and function, and that an intact SAR domain mediates MEC transformation exclusively in the cytoplasm, via a novel nontranscriptional mechanism, whereby the SAR motif is accessible for ligand and/or protein interactions. These findings are significant, since they provide novel molecular insights into the functions of ETS transcription factors in mammary cell transformation.
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U2 - 10.1186/1476-4598-10-103
DO - 10.1186/1476-4598-10-103
M3 - Article
C2 - 21871131
AN - SCOPUS:80052032237
SN - 1476-4598
VL - 10
JO - Molecular Cancer
JF - Molecular Cancer
M1 - 103
ER -