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

M Watanabe, Y Ogawa, K Ito, M Higashihara… - The American journal of …, 2003 - Elsevier
M Watanabe, Y Ogawa, K Ito, M Higashihara, ME Kadin, LJ Abraham, T Watanabe, R Horie
The American journal of pathology, 2003Elsevier
Overexpression of CD30 is the hallmark of Hodgkin and Reed-Sternberg (H-RS) cells and
drives constitutive nuclear factor-κB 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 …
Overexpression of CD30 is the hallmark of Hodgkin and Reed-Sternberg (H-RS) cells and drives constitutive nuclear factor-κB 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.
Elsevier