Epigenetic silencing of the RASSF1A tumor suppressor gene through HOXB3-mediated induction of DNMT3B expression.
The RASSF1A tumor suppressor gene is epigenetically silenced in a variety of cancers. Here, we perform a genome-wide human shRNA screen and find that epigenetic silencing of RASSF1A requires the homeobox protein HOXB3. We show that HOXB3 binds to the DNA methyltransferase DNMT3B gene and increases its expression. DNMT3B, in turn, is recruited to the RASSF1A promoter, resulting in hypermethylation and silencing of RASSF1A expression. DNMT3B recruitment is facilitated through interactions with Polycomb repressor complex 2 and MYC, which is bound to the RASSF1A promoter. Mouse xenograft experiments indicate that the oncogenic activity of HOXB3 is due, at least in part, to epigenetic silencing of RASSF1A. Expression analysis in human lung adenocarcinoma samples reveals that RASSF1A silencing strongly correlates with overexpression of HOXB3 and DNMT3B. Analysis of human cancer cell lines indicates that the RASSF1A epigenetic silencing mechanism described here may be common in diverse cancer types.
Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
Rajendra Kumar
RK
Palakurthy
Narendra
N
Wajapeyee
Manas K
MK
Santra
Claude
C
Gazin
Ling
L
Lin
Stephane
S
Gobeil
Michael R
MR
Green
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D015894:Genome, Human / Q000235:genetics; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051379:Mice; D063146:Polycomb-Group Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism; D000097584:DNA Methyltransferase 3B
D004248:DNA (Cytosine-5-)-Methyltransferases; D018398:Homeodomain Proteins; D063146:Polycomb-Group Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D025521:Tumor Suppressor Proteins; D000097584:DNA Methyltransferase 3B; C542921:HoxB3 protein, human; C411762:RASSF1 protein, human