RBP2‐H1/JARID1B is a transcriptional regulator with a tumor suppressive potential in melanoma cells

Abstract

The RBP2-H1/JARID1B nuclear protein belongs to the ARID family of DNA-binding proteins and is a potential tumor suppressor that is lost during melanoma development. As we have recently shown, one physiological function of RBP2-H1/JARID1B is to exert cell cycle control via maintenance of active retinoblastoma protein. We now add new evidence that RBP2-H1/JARID1B can also directly regulate gene transcription in a reporter assay system, either alone or as part of a multimolecular complex together with the developmental transcription factors FOXG1b and PAX9. In melanoma cells, chromatin immunoprecipitation combined with promoter chip analysis (ChIP-on-chip) suggests a direct binding of re-expressed RBP2-H1/JARID1B to a multitude of human regulatory chromosomal elements (promoters, enhancers and introns). Among those, a set of 23 genes, including the melanoma relevant genes CDK6 and JAG-1 could be confirmed by cDNA microarray analyses to be differentially expressed after RBP2-H1/JARID1B re-expression. In contrast, in nonmelanoma HEK 293 cells, RBP2-H1/JARID1B overexpression only evokes a minor transcriptional response in cDNA microarray analyses. Because the transcriptional regulation in melanoma cells is accompanied by an inhibition of proliferation, an increase in caspase activity and a partial cell cycle arrest in G1/0, our data support an anti-tumorigenic role of RBP2-H1/JARID1B in melanocytic cells. ' 2007 Wiley-Liss, Inc.Key words: melanoma; transcription; gene expression; retinoblastoma protein binding protein; apoptosisIn 1999, our group detected a gene transcript suppressed by UV-B in normal human melanocytes (Acc. No. AF087481, 1 ). Based on its homology to the previously described RBP2, 2 this new gene was termed retinoblastoma binding protein 2-homolog 1 (RBP2-H1). Subsequent expression studies revealed a frequent loss of RBP2-H1 in the majority of advanced and metastatic melanomas in vivo and in many melanoma cell lines, whereas benign melanocytic tumors, normal tissues and other cancer types mostly retain RBP2-H1. 1,3 Recently, we showed that RBP2-H1 has a tumor suppressive activity partly due to binding and stabilization of hypophosphorylated retinoblastoma protein (pRb) leading to maintenance of pRb-mediated cell cycle control. 4 As a result of truncation studies, we located the pRb-binding activity of RBP2-H1 to its C-term, containing a homolog region of the non-T/E1A-pRb binding domain known from other retinoblastoma binding proteins like RBP2. 5 Moreover, RBP2-H1 and its splicing variants PLU-1 and RBBP2H1a contain further well-conserved domains known to be involved in direct gene regulation and chromatin homeostasis, e.g. 3 PHD motifs and the ARID (AT-rich interacting) DNA-binding domain. [6][7][8][9] Although the 3 splicing variants show a cDNA sequence homology of more than 98%, RBP2-H1 differs from PLU-1 and RBBP2H1a by an additional exon encoding a region with strong homology to chromosomal ALU repeats. Thus, previously reported differences in tissue expression (PLU-1 shows a restricted expre...

Binding of the JmjC Demethylase JARID1B to LSD1/NuRD Suppresses Angiogenesis and Metastasis in Breast Cancer Cells by Repressing Chemokine CCL14

“…However, it has also been suggested that JARID1B itself has a tumor suppressive activity, partly, due to its binding and ability to stabilize hypophosphorylated pRb, leading to maintenance of pRb-mediated cell-cycle control (5). In agreement with this, it has been observed that the expression of JARID1B is lost in the majority of advanced and metastatic melanomas and in many melanoma cell lines (4,7). In this article, we showed that JARID1B is able to suppress angiogenesis and metastasis, supporting the notion that JARID1B itself is a potential tumor suppressor.…”

“…Subsequently, JARID1B dysregulation has been reported in several types of solid tumors, including prostate cancer (3), melanoma (4-7), and bladder cancer (8). Surprisingly, however, mechanistic studies on the role of JARID1B in different types of cancer have yielded inconsistent and even confusing results (1,3,5,(7)(8)(9)(10). Therefore, the mechanistic role of JARID1B in tumor progression remains an intriguing topic.…”

The role of components of the chromatin modification machinery in carcinogenesis of clear cell carcinoma of the ovary (Review)

“…pRb phosphorylation leads to cell release from G1 arrest and to promotion entry into the S-phase (36). In addition, JARID1B/ KDM5B, a member of the ARID family, exerts cell cycle control via maintenance of pRb (39). These data allow us to speculate that proteins of the ARID family directly or indirectly regulate the cell cycle, particularly alterations in the cell cycle checkpoint machinery.…”

Immunohistochemical detection and clinicopathological significance of JARID1B/KDM5B and P16 expression in invasive ductal carcinoma of the breast

“…In this study, we demonstrated that JARID1B/KDM5B expression was statistically significantly different between T1 and T3 (c 2 = 5.365, P < 0.05) and grade I and grade II (c 2 = 6.097, P < 0.05) tumors; that JARID1B/KDM5B protein expression in lymph node metastasis groups (N1, N2, N3) was significantly higher than in those tumors without lymph node involvement (N0) (c 2 = 4.295, c 2 = 5.814, and c 2 = 4.812, respectively; P < 0.05). Surprisingly, however, mechanistic studies on the role of JARID1B/KDM5B in different types of cancer have yielded inconsistent and even confusing results (Roesch et al, 2008(Roesch et al, , 2010. In melanocytic tumors, JARID1B/KDM5B was found to be highly expressed in benign nevi, which typically are characterized by oncogene-induced senescence.…”