The multiple myeloma SET domain (MMSET) protein is overexpressed in multiple myeloma (MM) patients with the translocation t(4;14). Although studies have shown the involvement of MMSET/ Wolf-Hirschhorn syndrome candidate 1 in development, its mode of action in the pathogenesis of MM is largely unknown. We found that MMSET is a major regulator of chromatin structure and transcrip- IntroductionMultiple myeloma is an incurable malignancy of mature plasma cells, associated in approximately 40% of cases with recurrent chromosomal translocations that lead to overexpression of known and putative oncogenes. 1,2 MMSET (WHSC1, NSD2) is linked to the immunoglobulin promoter/enhancer in t(4;14) translocations, found in 15%-20% of multiple myeloma. 3 Chromosomal fusion leads to overexpression of MMSET and FGFR3 genes; however, approximately 30% of the patient samples overexpress only the MMSET gene, suggesting its pivotal role in the disease. [4][5][6] The other nuclear receptor Su(var)3-9, Enhancer-of-zeste, Trithorax (SET) domain-containing (NSD) family members, NSD1 and NSD3, were both found to be rearranged as fusion proteins with NUP98 in rare cases of acute myeloid leukemia, and NSD3 is overexpressed in breast cancer, 7,8 suggesting that deregulation of these proteins plays a causative role in malignancy. The MMSET gene undergoes complex alternative splicing and differential promoter usage, giving rise to a number of different transcripts from the locus, most of which are overexpressed in t(4;14) myelomas ( Figure 1A). 2,9,10 The protein domains found in full-length MMSET include 2 conserved Pro-Trp-Trp-Pro motif (PWWP) domains, 4 plant homeo domain fingers, and 1 SET domain, all of which are commonly found in transcriptional regulators. 11,12 Our previous report suggested that MMSET may be part of a corepressor complex. 13 SET domain-containing proteins can methylate lysine residues on histone tails. 14 Methylation and other covalent modifications of histone tails, such as acetylation, phosphorylation, ubiquitination, or sumoylation, can alter gene expression depending on the residue altered, the type of the modification, and whether the modified histone residue is found in a gene promoter, enhancer, or the body of a gene. 15 Promoters of actively transcribed genes are marked by the presence of H3K4me3, whereas the transcribed body of active genes is characterized by methylation at H3K36 (H3K36me3). 16,17 By contrast, CpG islands are depleted of H3K36 methylation. 18 Inactive and silenced genes show methylation at H3K27me3 and H3K9me3, respectively. 16,17,19 Previous reports suggested promiscuous activity of the SET domains of the NSD family proteins. NSD1 was initially shown to methylate both H3 and H4 histones, and more recently its specificity has been narrowed down to lysine 36 on histone H3. 8 Likewise, MMSET was able to methylate both H3 and H4 histones in vitro. 13,20 A recent report showed that the histone methyl-transferase (HMT) activity of NSD proteins is substrate specific, helping explain these discrepa...

MMSET, identified by its fusion to the IgH locus in t( IntroductionMultiple myeloma (MM) is associated with recurrent chromosomal translocations that link the immunoglobulin promoter/enhancer with several partner genes, deregulation of which likely plays a key role in disease pathogenesis. MMSET (multiple myeloma SET domain) was identified as a gene involved in the t(4;14)(p16;q32) translocation present in approximately 15% to 20% of MM. 1,2 This subtype of myeloma has a poor prognosis with frequent relapse after autologous stem-cell transplantation. [3][4][5] The breakpoint within 14q32.3 occurs in the immunoglobulin switch region and dissociates the intronic enhancer (E) from the 3Ј enhancer (E). The 4p16.3 breakpoint falls centromeric to the fibroblast growth factor receptor 3 (FGFR3) gene, placing it adjacent to the strong 3Ј enhancer on the derivative chromosome 14. Concurrently, the intronic enhancer on derivative chromosome 4 is juxtaposed to the MMSET gene. The breakpoint on chromosome 4 can vary in different cases and can yield transcripts that can exclude up to 6 of the initial exons of MMSET. 1 As a result of the translocation, both FGFR3 and MMSET can be deregulated; however, microarray analysis of t(4;14)-associated myeloma showed that all cases overexpress MMSET, but up to 25% of these cases do not overexpress FGFR3, implying a critical role for MMSET in this subset of myeloma. 4,6 The MMSET gene, also known as Wolf-Hirschhorn Syndrome Candidate 1 (WHSC1) 2 or Nuclear Receptor-binding SET Domain 2 (NSD2), 7 spans 120 kb, consists of 24 exons and undergoes complex alternative splicing. Two major transcripts were identified: type I encodes a protein of 647 amino acids and type II encodes a protein of 1365 amino acids. 1 Both proteins share a common amino terminus. A third transcript initiated within a middle intron of MMSET, encoding a mRNA comprising the 3Ј half of the MMSET gene was identified 8 and encodes a protein named RE-IIBP.The 1365 amino acid MMSET protein contains a SET domain that is found in many histone methyltransferases (HMTs) and determines their enzymatic activity. Histone methylation of chromatin yields docking sites for modules found on transcriptional regulators, attracting these proteins to chromatin. Depending on the histone site modified and genetic context, methylation may be associated with activation or repression of genes. 9 Other potential functional motifs in the MMSET proteins include nuclear localization signals (NLSs), an HMG box (high mobility group) often representing a DNA-binding domain, 2 PWWP domains 2,10 (proline-tryptophan-tryptophanproline) found in other nuclear proteins and 4 PHD (plant homeodomain) zinc fingers recently defined as binding modules for methylated lysines. 11,12 We found that the MMSET protein is strikingly up-regulated in myeloma cell lines harboring t(4;14). MMSET is concentrated in the nucleus, has specific HMT activity against core histones H3 and H4, and coimmunoprecipitates and interacts functionally with corepressors and histone For pe...

Outcome for children with childhood acute lymphoblastic leukemia (ALL) who relapse is poor. To gain insight into the mechanisms of relapse, we analyzed gene-expression profiles in 35 matched diagnosis/relapse pairs as well as 60 uniformly treated children at relapse using the Affymetrix platform. Matched-pair analyses revealed significant differences in the expression of genes involved in cell-cycle regulation, DNA repair, and apoptosis between diagnostic and earlyrelapse samples. Many of these pathways have been implicated in tumorigenesis previously and are attractive targets for intervention strategies. In contrast, no common pattern of changes was observed among late-relapse pairs. Earlyrelapse samples were more likely to be similar to their respective diagnostic sample while we noted greater divergence in gene

The viscosities of CaO-SiO 2 -20 wt%Al 2 O 3 -MgO slags (CaO/SiO 2 ¼ 1.0-1.2, wt%MgO ¼ 5-13) were measured to estimate the effect of MgO on the viscous behaviour at elevated temperatures. The slag viscosity at 1773 K decreased with increasing MgO contents, which was typical of a basic oxide component at relatively low basicity (CaO/SiO 2 ) of 1.0. The FT-IR spectroscopic analysis of the slag structure seems to verify this behaviour. However, an unexpected contradiction with the temperature dependence was observed above 10 wt%MgO and above CaO/SiO 2 of 1.2. Although the apparent activation energy was expected to decrease with additions of the basic oxide component MgO, the apparent activation energy increased. This unexpected behaviour seems to be related to the change in the primary phase field correlating to the phase diagram corresponding to the slag composition. Therefore, in order to understand the viscosity at both high Al 2 O 3 and MgO, not only should the typical depolymerization of the slag structure with high MgO content be considered but also the primary phases of which the molten slag originates. steel research int. 81 (2010) No. 4 Process Metallurgy 14 12 10 8 6 4 2 0 0 50 100 150 200 250 300 350 Melilite Spinel CaO-SiO 2 -20Al 2 O 3 -MgO slags C/S=1.0 C/S=1.2 CaO-SiO 2 -Al 2 O 3 slags after Machin et al. C/S=0.8 C/S=1.0 CaO-SiO 2 -Al 2 O 3 -MgO slags after Shankar et al. 1.98-5.01 wt% MgO, 21.2-28.5 wt% Al 2 O 3 CaO-SiO 2 -Al 2 O 3 -MgO slags after Saito et al. C/S=1.0, 17-18 wt% Al 2 O 3 Activation energy (kJ/mol) wt% MgO Figure 5. The change of activation energy in CaO-SiO 2 -Al 2 O 3 -MgO slags as a function of wt%MgO.

The FT-IR spectra of the CaO-SiO 2 and CaO-SiO 2 -CaF 2 slags were measured to understand the structural aspects of (fluoro-) silicate systems. The relative intensity of Si-O rocking band is very strong at SiO 2 saturation condition and this band disappears in the composition greater than 44.1 (mol%) CaO in the CaO-SiO 2 binary system. The bands for [SiO 4 ]-tetrahedra at about 1 150-760 cm Ϫ1 split up with increasing content of CaO greater than 44.1 mol%. The IR bands in this wavenumber range are divided into four groups, that is about 1090, 990, 920, and 870 cm Ϫ1 , which have been assigned to NBO/Siϭ1, 2, 3, and 4, respectively. In the CaO-SiO 2 -CaF 2 (2CaO · SiO 2 -Satd.) system, the center of gravity of the bands at about 1 170-710 cm Ϫ1shifts from about 980 to 850 cm Ϫ1 by increasing the ratio X CaF 2 /X SiO 2 from 0.22 to 0.64. The bands for [SiO 4 ]-tetrahedra are observed from about 1 070 to 730 cm Ϫ1 in the CaO-17.6(mol%)SiO 2 -CaF 2 system, while these bands are observed from about 1 120 to 720 cm Ϫ1 in the CaO-40.0(mol%)SiO 2 -CaF 2 system. The effect of substitution of CaF 2 for CaO on the depolymerization of silicate network is observed to significantly depend on the SiO 2 content in the slags. The bands for [SiO 4 ]-tetrahedra are observed from about 1 110 to 720 cm Ϫ1 in the CaO-SiO 2 -14.1(mol%)CaF 2 system and the center of gravity of these bands shifts from about 990 to 850 cm Ϫ1 with increasing CaO/SiO 2 ratio. The fraction of the relatively depolymerized units continuously increases from about 0.5 to 0.8 as the composition of slags changes from 2CaO · SiO 2 to CaO saturation condition.