AP-1 mediated relief of repressive activity of the CD30 promoter microsatellite in Hodgkin and Reed-Sternberg cells.
Overexpression of CD30 is the hallmark of Hodgkin and Reed-Sternberg (H-RS) cells and drives constitutive nuclear factor-kappaB activation that is the molecular basis for the pathophysiology of Hodgkin's lymphoma. Transcription of the CD30 gene is controlled by the core promoter that is driven by Sp-1 and the microsatellite sequences (MSs) that represses core promoter activity. To understand the mechanism(s) of CD30 overexpression in H-RS cells, we structurally and functionally characterized the CD30 MSs. Although the CD30 MS of H-RS cell lines was polymorphic, it was not truncated compared with that of control cells. A strong core promoter activity and constitutive Sp-1 binding were revealed in all cell lines examined irrespective of the levels of CD30 expression. In transient reporter gene assays, all MS clones derived from H-RS cell lines repressed the core promoter activity in unrelated cell lines, but not in the H-RS cell lines. An AP-1-binding site was found in the MS at nucleotide position of -377 to -371, the presence of which was found to relieve repression of the core promoter in H-RS cell lines but not in other tumor cell lines. H-RS cell lines showed constitutive and strong AP-1-binding activity, but other cell lines did not. The AP-1 complex contained JunB, whose overexpression activated reporter constructs driven by the CD30 promoter including the MSs, and was dependent on the AP-1 site. JunB expression was detected in H-RS cells in vitro and in vivo, but not in reactive cells or tumor cells of non-Hodgkin's lymphoma of diffuse large B-cell type. Transduction of JunB small interfering RNAs suppressed CD30 promoter activity in L428 cells but not in control cells. Taken together, overexpression and binding of JunB to the AP-1 site appear to relieve the repression of the core promoter by the CD30 MS in H-RS cells, which provide one basis for the constitutive overexpression of CD30 in Hodgkin's lymphoma.
Watanabe
Mariko
M
Fourth Department of Internal Medicine, Kitasato University School of Medicine, Kanagawa, Japan.
Ogawa
Yuji
Y
Ito
Kinji
K
Higashihara
Masaaki
M
Kadin
Marshall E
ME
Abraham
Lawrence J
LJ
Watanabe
Toshiki
T
Horie
Ryouichi
R
D001665:Binding Sites; D002460:Cell Line; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006689:Hodgkin Disease / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017730:Ki-1 Antigen / Q000235:genetics* / Q000378:metabolism; D018895:Microsatellite Repeats; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D016539:Reed-Sternberg Cells / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D017730:Ki-1 Antigen; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1