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This Article Accepted manuscript (PDF) All Versions of this Article: ERC-08-0060v1 15/3/817    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Zhou, C. Articles by Melmed, S. Search for Related Content PubMed PubMed Citation Articles by Zhou, C. Articles by Melmed, S.

C Zhou, Medicine, Cedars Sinai Medical Center, Los Angeles, United States
Y Tong, Medicine, Cedars Sinai Medical Center, Los Angeles, United States
K Wawrowsky, Medicine, Cedars Sinai Medical Center, Los Angeles, United States
S Bannykh, Pathology, Cedars Sinai Medical Center, Los Angeles, United States
I Donangelo, Medicine, Cedars Sinai Medical Center, Los Angeles, United States
S Melmed, Medicine, Cedars Sinai Medical Center, Los Angeles, United States

Correspondence: Shlomo Melmed, Email: melmed{at}csmc.edu

Abstract

As hPTTG1 is up-regulated in endocrine tumors, we studied regulatory mechanisms for hPTTG1 expression. We identified Oct-1 binding motifs in the hPTTG1 promoter region and show Oct-1 specific binding to the hPTTG1 promoter using Chromatin Immunoprecipitation. We overexpressed Oct-1 and observed 2.5-fold activation of hPTTG1 promoter luciferase constructs (-2642/-1 and -1717/-1). Transcriptional activation was abrogated by cotransfection of an inactive Oct-1 form lacking the POU domain, or by utilizing mutated hPTTG1 promoters, or mutants devoid of two Oct-1 binding motifs (-1717/-1mut, -637/-1 or -433/-1). Using biotin-streptavidin pull-down assays, we confirmed Oct-1 binding to the two octamer motifs in the hPTTG1 promoter (-1669/-1631 and -1401/-1361). Endogenous hPTTG1 mRNA and protein increased up to 4-fold in Oct-1 transfectants, as measured by real-time PCR and Western blot. In contrast, siRNA mediated suppression of endogenous Oct-1 attenuated both hPTTG1 mRNA and protein levels. Using confocal immunofluorescent imaging, Oct-1 and hPTTG1 were concordantly upregulated in pituitary (57% and 62%, n=79, p<0.01) and breast tumor specimens (57% and 42%, n=77, p<0.05) respectively. The results show that Oct-1 transactivates hPTTG1, and both proteins are concordantly overexpressed in endocrine tumors, thus offering a mechanism for endocrine tumor hPTTG1 abundance.