Project description:The MMSET (Multiple Myeloma SET domain) protein is overexpressed in multiple myeloma patients with the translocation t(4;14). Although studies have shown the involvement of MMSET/WHSC1 in development, its mode of action in the pathogenesis of multiple myeloma (MM) is largely unknown. We found that MMSET is a major regulator of chromatin structure and transcription in t(4;14) MM cells. High levels of MMSET correlate with an increase in lysine 36 methylation of histone H3 and a decrease in lysine 27 methylation across the genome, leading to a more open structural state of the chromatin. Loss of MMSET expression alters adhesion properties, suppresses growth and induces apoptosis in MM cells. Consequently, genes affected by high levels of MMSET are implicated in the p53 pathway, cell cycle regulation and integrin signaling. Regulation of many of these genes required functional histone methyl-transferase (HMT) activity of MMSET. These results implicate MMSET as a major epigenetic regulator in t(4;14)+ MM.
Project description:The MMSET (Multiple Myeloma SET domain) protein is overexpressed in multiple myeloma patients with the translocation t(4;14). Although studies have shown the involvement of MMSET/WHSC1 in development, its mode of action in the pathogenesis of multiple myeloma (MM) is largely unknown. We found that MMSET is a major regulator of chromatin structure and transcription in t(4;14) MM cells. High levels of MMSET correlate with an increase in lysine 36 methylation of histone H3 and a decrease in lysine 27 methylation across the genome, leading to a more open structural state of the chromatin. Loss of MMSET expression alters adhesion properties, suppresses growth and induces apoptosis in MM cells. Consequently, genes affected by high levels of MMSET are implicated in the p53 pathway, cell cycle regulation and integrin signaling. Regulation of many of these genes required functional histone methyl-transferase (HMT) activity of MMSET. These results implicate MMSET as a major epigenetic regulator in t(4;14)+ MM. Total RNA was isolated from two different systems: an inducible knock down designed in the 5' region of MMSET. Upon addition of doxycycline we block MMSET expression. The second system we used was a repletion system. By retroviral infection of knock out cells for MMSET we restored the expression of MMSET wild type and two mutants of the protein: one active and one catalytically inactive. Triplicates of each sample were analyzed.
Project description:We investigated gene expression in isogenic myeloma cell lines with or without overexpressed MMSET protein. MMSET is a histone methyltransferase which methylates lysine 36 on histone H3. Overexpression of MMSET in myeloma leads to a global increase in H3K36 methylation and concomitant decrease in H3K27 methylation. These global changes in histone methylation lead to altered gene expression.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.