20 ng of total RNA was amplified and labeled using Ovation RNA amplification system V2 (NuGEN)
20 ng of total RNA was amplified and labeled using Ovation RNA amplification system V2 (NuGEN). H3K79 methylation is enhanced at many loci in leukemia cells from a murine model of Mll-AF4 and in human MLL-AF4 leukemia cells and this elevation is correlated with enhanced gene expression. Furthermore, suppression of H3K79 methylation leads to inhibition of gene expression in MLL-AF4 cells. These data demonstrate that inhibition of DOT1L may be a therapeutic approach in this disease, and that this mouse model should be useful for assessment of therapeutic approaches forMLL-rearranged ALL. == Introduction == Leukemias mediated byMLL-rearrangements possess unique clinical and biological features.MLL-rearrangements can be found in Acute Lymphoblastic Leukemias (ALL), Acute Myeloid Leukemias (AML) and acute biphenotypic or Mixed Lineage Leukemias (MLL).MLL-translocations are present NMDA-IN-1 in over 70% of cases of infant leukemias (Biondi et al., 2000) and in general account for approximately 5% of ALL, 510% of AML, and NMDA-IN-1 a significant portion of acute biphenotypic or mixed-lineage leukemias (Huret et al., 2001). Patients withMLL-rearranged ALL have a particularly unfavorable prognosis as compared to other forms of ALL (Chen et al., 1993). To date more than 50 MLL fusion partner genes have been reported (Ayton NMDA-IN-1 and Cleary, 2001;Krivtsov and Armstrong, 2007). The t(4;11)(q21;q23) encodes MLL-AF4 and is the most frequentMLL-translocation found in ALL. Multiple mouse models have been developed that recapitulateMLL-rearranged AML (reviewed in (Ayton and Cleary, 2001). However, development of models that faithfully recapitulate MLL-fusion mediated ALL has proven more difficult. ConstitutiveMll-AF4knock-in resulted in mixed lymphoid/myeloid hyperplasia and mature B-cell neoplasms in mice (Chen et al., 2006). Conditional expression ofMll-AF4based on interchromosomal recombination in lymphoid lineages produced mature B-cell lymphomas (Metzler et al., 2006). Thus further development of murine models ofMLL-rearranged ALL is needed. MLL is a mammalian homologue ofDrosophilatrithorax and possesses multiple functional domains, including amino-terminal AT hooks that bind DNA and a carboxyl-terminal Su(var)39, Enhancer-of-zeste, NMDA-IN-1 Trithorax (SET) domain that methylates lysine 4 of histone H3 (H3K4). H3K4 methylation is associated with transcriptional activation (reviewed in (Shilatifard, 2006), and MLL positively regulates expression of clustered Homeobox (HOX) and other genes during development, at least in part via H3K4 methylation (Milne et al., 2002;Nakamura et al., 2002). Mll has important roles in development including hematopoietic development (Hess et al., 1997;Jude et al., 2007) MLL-translocations invariably encode fusion proteins that have lost the H3K4 methyltransferase (SET) domain. However MLL-fusion proteins retain the ability to bindHOXgenes and other promoter regions and are associated with Rabbit Polyclonal to SLC39A1 enhanced gene expression (Armstrong et al., 2002;Guenther et al., 2005;Rozovskaia et al., 2001;Yeoh et al., 2002;Zeisig et al., 2004). Several mechanisms have been proposed as to how MLL-fusions may deregulate gene appearance including recruitment of unusual histone modification actions (Cheung et al., 2007;Krivtsov and Armstrong, 2007;Okada et al., 2005). For instance, MLL-AF10 and MLL-ENL have already been proven to recruit the non-SET domains methyltransferase DOT1L which promotes methylation of histone H3 lysine 79 (H3K79) on theHoxA9promoter (Mueller et al., 2007;Okada et al., 2005;Zeisig et al., 2005). Since H3K79 methylation is normally associated with positive transcriptional legislation NMDA-IN-1 (Schubeler et al., 2004;Shilatifard, 2006), DOT1L mediated methylation of H3K79 may donate to improved expression ofHOXA9in MLL-ENL and MLL-AF10 induced leukemias. Furthermore, AF10, ENL and various other MLL-fusion partners such as for example AF4 and AF9 are usually within nuclear complexes connected with DOT1L (Bitoun et al., 2007;Mueller et al., 2007;Okada et al., 2005;Zeisig et al., 2005;Zhang et al., 2006). Hence aberrant recruitment of DOT1L towards the promoters of MLL focus on genes could be a common feature of several oncogenic MLL-fusion proteins. Nevertheless, the level of H3K79 methylation adjustments as well as the specificity of the epigenetic adjustments forMLL-rearranged leukemias never have been defined. Right here, we report the introduction of a murine model where conditional appearance of MLL-AF4 induces both ALL and AML. Genome wide evaluation of gene appearance and H3K79 methylation shows that.