The BRAF V600E mutation causes impaired expression of sodium iodide symporter (NIS) and radioiodine refractoriness of thyroid cancer, but the underlying mechanism remains undefined. In this study, we hypothesized that histone deacetylation at the NIS (SLC5A5) promoter was the mechanism. Using the chromatin immunoprecipitation approach, we examined histone acetylation status on the lysine residues H3K9/14, H3K18, total H4, and H4K16 at the NIS promoter under the influence of BRAF V600E. We found that expression of stably or transiently transfected BRAF V600E inhibited NIS expression while the deacetylase inhibitor SAHA stimulated NIS expression in PCCL3 rat thyroid cells. Although BRAF V600E enhanced global histone acetylation, it caused histone deacetylation at the NIS promoter while SAHA caused acetylation in the cells. In human thyroid cancer BCPAP cells harboring homozygous BRAF V600E mutation, BRAF V600E inhibitor, PLX4032, and MEK inhibitor, AZD6244, increased histone acetylation of the NIS promoter, suggesting that BRAF V600E normally maintained histone in a deacetylated state at the NIS promoter. The regions most commonly affected with deacetylation by BRAF V600E were the transcriptionally active areas upstream of the translation start that contained important transcription factor binding sites, including nucleotides -297/-107 in the rat NIS promoter and -692/-370 in the human NIS promoter. Our findings not only reveal an epigenetic mechanism for BRAF V600E-promoted NIS silencing involving histone deacetylation at critical regulatory regions of the NIS promoter but also provide further support for our previously proposed combination therapy targeting major signaling pathways and histone deacetylase to restore thyroid gene expression for radioiodine treatment of thyroid cancer.
Pubmed ID: 24243688 RIS Download
Publication data is provided by the National Library of Medicine ® and PubMed ®. Data is retrieved from PubMed ® on a weekly schedule. For terms and conditions see the National Library of Medicine Terms and Conditions.
TESS is a web tool for predicting transcription factor binding sites in DNA sequences. It can identify binding sites using site or consensus strings and positional weight matrices from the TRANSFAC, JASPAR, IMD, and our CBIL-GibbsMat database. You can use TESS to search a few of your own sequences or for user-defined CRMs genome-wide near genes throughout genomes of interest. Search for CRMs Genome-wide: TESS now has the ability to search whole genomes for user defined CRMs. Try a search in the AnGEL CRM Searches section of the navigation bar.. You can search for combinations of consensus site sequences and/or PWMs from TRANSFAC or JASPAR. Search DNA for Binding Sites: TESS also lets you search through your own sequence for TFBS. You can include your own site or consensus strings and/or weight matrices in the search. Use the Combined Search under ''Site Searches'' in the menu or use the box for a quick search. TESS assigns a TESS job number to all sequence search jobs. The job results are stored on our server for a period of time specified in the search submit form. During this time you may recall the search results using the form on this page. TESS can also email results to you as a tab-delimited file suitable for loading into a spreadsheet program. Query for Transcription Factor Info: TESS also has data browsing and querying capabilities to help you learn about the factors that were predicted to bind to your sequence. Use the Query TRANSFAC or Query Matrices links above or use the search interface provided from the home page.
View all literature mentions