A tissue-restricted cAMP transcriptional response: SOX10 modulates alpha-melanocyte-stimulating hormone-triggered expression of microphthalmia-associated transcription factor in melanocytes.
alpha-Melanocyte-stimulating hormone (MSH) utilizes cAMP to trigger pigmentation of melanocytes via activation of melanocyte-restricted microphthalmia-associated transcription factor (M-MITF) expression. M-MITF is a melanocyte-restricted helix-loop-helix transcription factor capable of transactivating promoters for multiple genes whose products modulate pigmentation. Although M-MITF promoter activation by MSH is known to occur through a conserved cAMP-response element (CRE), it remains unclear how this CRE exhibits such exquisitely tissue-restricted responsiveness. Here we show that cAMP-mediated CRE-binding protein activation of the M-MITF promoter requires a second DNA element located approximately 100 bp upstream, a site that is bound and activated by SOX10. Mutations in the SOX10 transcription factor, like MITF, results in a disorder known as Waardenburg Syndrome. The cAMP response of the M-MITF promoter was analyzed in melanoma and neuroblastoma cells (which are neural crest-derived but lack both M-MITF and SOX10 expression). M-MITF promoter responsiveness to cAMP was found to depend upon SOX10, and reciprocally, SOX10 transactivation was dependent upon the CRE. Ectopic SOX10 expression, in cooperation with cAMP signaling, activated the M-MITF promoter function and the expression of measurable endogenous M-MITF transcripts in neuroblastoma cells. SOX10dom, a mutant allele, failed to cooperate with cAMP in neuroblastoma cells and attenuated the cAMP responsiveness of the M-MITF promoter in melanoma cells. These observations demonstrate a means whereby the ubiquitous cAMP signaling machinery is harnessed to produce a highly tissue-restricted transcriptional response by cooperating with architectural factors, in this case SOX10.
Huber
Wade E
WE
Division of Pediatric Hematology/Oncology, Dana-Farber Cancer Institute and Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Price
E Roydon
ER
Widlund
Hans R
HR
Du
Jinyan
J
Davis
Ian J
IJ
Wegner
Michael
M
Fisher
David E
DE
D000483:Alleles; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D005822:Genetic Vectors; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008544:Melanocytes / Q000378:metabolism*; D051739:Microphthalmia-Associated Transcription Factor; D008957:Models, Genetic; D009154:Mutation; D009447:Neuroblastoma / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055757:SOXE Transcription Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D000521:alpha-MSH / Q000378:metabolism*
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; C527923:SOX10 protein, human; D055757:SOXE Transcription Factors; D014157:Transcription Factors; D000521:alpha-MSH; D000242:Cyclic AMP; D008156:Luciferases