AP-1 mediated relief of repressive activity of the CD30 promoter microsatellite in Hodgkin and Reed-Sternberg cells.

Abstract

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.

• Authors: Mariko Watanabe, Yuji Ogawa, Kinji Ito, Masaaki Higashihara, Marshall E Kadin, Lawrence J Abraham, Toshiki Watanabe, Ryouichi Horie
• Journal: The American journal of pathology (Am J Pathol) Vol. 163 Issue 2 Pg. 633-41 (Aug 2003) ISSN: 0002-9440 [Print] United States
• PMID: 12875982 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Ki-1 Antigen
• Proto-Oncogene Proteins c-jun
• RNA, Small Interfering
• Transcription Factor AP-1

Topics

• Binding Sites
• Cell Line
• Gene Expression Regulation
• Genes, Reporter
• Hodgkin Disease (genetics, metabolism)
• Humans
• Ki-1 Antigen (genetics, metabolism)
• Microsatellite Repeats
• Promoter Regions, Genetic
• Protein Binding
• Proto-Oncogene Proteins c-jun (genetics, metabolism)
• RNA, Small Interfering
• Reed-Sternberg Cells (physiology)
• Transcription Factor AP-1 (metabolism)