Breast cancer associated transcriptional repressor PLU‐1/JARID1B interacts directly with histone deacetylases

Abstract

The PLU-1/JARID1B nuclear protein, which is expressed in a high proportion of breast cancers, but shows restricted expression elsewhere, belongs to the ARID family of proteins, known to play important roles in development, differentiation, transcriptional regulation and chromatin remodeling. PLU-1/JARID1B is a strong transcriptional repressor, and here we show that the protein localizes in MAD bodies when cotransfected with class IIa histone deacetylases (HDACs) or N-CoR. Direct binding to class I and class IIa HDACs is demonstrated, while the interaction with N-CoR appears to be indirect. The domains involved in the HDAC4-PLU-1/JARID1B interaction were investigated in detail, and the data show that 2 PHD domains in PLU-1/JARID1B, which are involved in transcriptional repression, are also crucial for binding to a domain in the 5 0 region of HDAC4, overlapping the MEF-2 binding region. Physiological relevance of this interaction in the mammary gland is suggested from the observation that HDAC4 and PLU-1/JARID1B are coexpressed in the pregnant and involuting mouse mammary gland and are both silenced at lactation. Significantly, the expression of both proteins is seen in breast cancers. ' 2007 Wiley-Liss, Inc.Key words: PLU-1/JARID1B; breast cancer; transcriptional repression; histone deacetylasesThe PLU-1 gene was identified in a differential screen for genes that were down-regulated when HER2 signaling was inhibited. 1 However, PLU-1 has since been demonstrated to be expressed in 90% of breast carcinomas, regardless of the level of HER2 expression, and appears to be associated with malignant progression.2 In normal human adult tissues, the highest levels of expression of PLU-1 mRNA are seen in testis 1,3 with low levels of expression being observed in placenta, lymph node, and thymus.2 In the normal mammary gland, mPlu-1 mRNA is expressed in the embryo in the developing mammary bud, and at pregnancy in the adult, 4 suggesting a role in proliferation in the developing and differentiating tissue.The PLU-1 protein sequence contains several well-conserved domains known to be involved in protein interactions, gene regulation, and chromatin remodeling. These include 3 PHD domains, 5,6 the ARID domain (AT-rich interacting domain), 7 and 2 potential hormone-binding motifs. 8 The novel Trp/Tyr/Cys domain (overlapping the JmjC domain and renamed the PLU domain 9 ) interacts with a conserved motif found in 2 unrelated transcription factors (BF1 and PAX9).10 Thus, the protein could be recruited to DNA directly through the ARID DNA binding domain, or through other transcription factors.Within the larger ARID family of proteins, PLU-1 has been placed in the JARID1 subclass which contains 4 proteins, characterized by the presence of the JmjN and JmjC domains.11 Consequently, PLU-1 is now referred to as PLU-1/JARID1B. The 4 members of the JARID1 subclass show high conservation of sequence, but appear to have different profiles of expression and different functions. The RBBP2 (JARID1A) protein contains the canonical LXCXC domain...

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

“…A reasonable explanation for the discrepancy could be that the main part of the detected RBP2-H1-DNA interactions is not directly involved into transcriptional regulation of the corresponding genes, but rather affects other mechanisms of nuclear homeostasis, such as regulation of chromatin structure via histone methylation, as it has been recently suggested for PLU-1/JARID1B and RBP2/JARID1A. 6,7,11,65,66 Posttranslational modification of chromatin by histone methylation has wide-ranging effects on nuclear function, including maintenance of genome integrity, epigenetic inheritance and, of course, transcriptional regulation. 6 Thereby, the regulated genes do not necessarily have to be located in close relationship up-or downstream to the regulatory chromosomal element.…”

“…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 expression in most normal tissues and a marked upregulation in breast cancer) or possible variations in protein function of RBP2-H1 and PLU-1 would be explicable.…”

“…3,10 However, since all splicing variants include ARID, they have been recently grouped into the superfamily of ARID DNA-binding proteins, specifically into the JARID1B subgroup, characterized by an additional presence of the JmjN and JmjC domain, which has been defined as a histone demethylase motif involved in chromatin remodeling. 7,11,12 Consequently, RBP2-H1 is now referred as RBP2-H1/JARID1B and PLU-1 as PLU-1/JARID1B, respectively. However, especially for RBP2-H1/JARID1B, detailed data on its role in gene regulation are still lacking.…”

T cells reactive with HLA‐A*0201 peptides from the histone demethylase JARID1B are found in the circulation of breast cancer patients

“…[7][8][9][10][11] More recently, expression of this gene in other cancers (bladder, lung, AML) has been reported and the restricted expression in normal tissues confirmed 12 suggesting a specific involvement of PLU-1/JAR-ID1B in malignancy. Moreover, the restricted expression in adult tissues makes the protein a potential therapeutic target, particularly in women.…”

“…[7][8][9][10] The expression of JARID1B RNA is highest in ER þ ductal carcinomas (www.oncomine.org/), being less well expressed in lobular carcinomas 8 (see Fig. 1).…”