Expression of gp100 and CDK2 in melanoma cells is not co-regulated by a shared promoter region.
Expression of the pigmentation-associated gene PMel17 is regulated by a 1 kB promoter region shared between the PMel17 and CDK2 genes. The encoded melanosomal glycoprotein gp100 and the cell cycle regulatory protein CDK2 are transcribed in opposite directions. Luciferase reporter constructs were generated for subregions of the promoter containing 0, 1, 2 or 3 putative binding sites for transcription factors with basic helix-loop-helix (bHLH) motifs. The potential contribution of bHLH transcription factor microphthalmia transcription factor (MITF) to promoter activity was investigated by re-introducing microphthalmia into melanoma cells lacking expression. A bi-directional reporter construct was generated to investigate potential co-regulation of gp100 and CDK2 transcription. Promoter activity was assessed in presence and absence of phorbol ester tetradecanoyl phorbol 13-acetate (TPA). FACS analysis and immunohistology served to evaluate co-regulation of gp100 and CDK2 expression at the protein level. The full-length promoter, including a consensus binding site for MITF was found to contain sequences that suppressed gp100 expression. Introduction of MITF into non-expressing 1123 melanoma cells did not restore gp100 expression levels. A lack of coregulation for gp100 and CDK2 as suggested by immunostaining was supported by findings of dissimilar expression regulation by TPA for either gene. The current study provides insight into transcriptional regulation of the PMel17 and CDK2 genes, important to identify strategies for modulating expression of gp100 and CDK2 proteins by melanoma cells.
Stennett
Lawrence S
LS
Cardinal Bernardin Cancer Center, Loyola University Chicago, Maywood, IL, USA.
Riker
Adam I
AI
Kroll
Tara M
TM
ChaMberlin
Janine
J
Miki
Toru
T
Nickoloff
Brian J
BJ
Le Poole
I Caroline
IC
D042846:CDC2-CDC28 Kinases / Q000096:biosynthesis* / Q000235:genetics; D002273:Carcinogens / Q000494:pharmacology; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D051739:Microphthalmia-Associated Transcription Factor; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D058951:gp100 Melanoma Antigen
D002273:Carcinogens; D004268:DNA-Binding Proteins; C497234:MITF protein, human; D008562:Membrane Glycoproteins; D051739:Microphthalmia-Associated Transcription Factor; D009363:Neoplasm Proteins; C548637:PMEL protein, human; D011506:Proteins; D014157:Transcription Factors; D058951:gp100 Melanoma Antigen; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D013755:Tetradecanoylphorbol Acetate