Project description:MLL5 is a novel trithorax group gene and a candidate tumor suppressor gene located within a 2.5 Mb interval of chromosome band 7q22 that is frequently deleted in human myeloid malignancy. Here we show that Mll5 is required for normal hematopoietic stem cell (HSC) homeostasis. Inactivation of the Mll5 gene in mice results in reduced cellularity of the long-term HSC compartment, which correlates with functional impairment of long-term repopulation potential under competitive conditions. Bone marrow cells from Mll5-deficient mice were defective in spleen colony-forming assays, and the mutant mice showed enhanced susceptibility to 5-Fluorouracil-induced myelosuppression. Heterozygous and homozygous Mll5 mutant mice did not spontaneously develop hematologic cancers, and loss of Mll5 did not alter the phenotype of a fatal myeloprolferative disorder induced by oncogenic Kras in vivo. Collectively, the data reveal an important role for Mll5 in HSC homeostasis, and provide a basis for further studies to explore its role in leukemogenesis. Keywords: Cell type comparision.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes. Mouse hematopoietic stem cells were purified from bone marrow cells using negative and positive selection with a Magnetic-Activated Cell Sorter (MACS). total RNA and mRNA were purified from the purified cells using Trizol reagent and magnetic oligo dT beads. Double strand cDNAs were synthesized using a cDNA synthesis kit and anchored oligo dT primers. After NlaIII digestion, 3’ cDNAs were isolated and amplified through 16-cycle PCR. SAGE tags were released from the 3’ cDNA after linker ligation. Ditags were formed, concatemerized and cloned into a pZERO vector. Sequencing reactions were performed with the ET sequencing terminator kit. Sequences were collected using a Megabase 1000 sequencer. SAGE tag sequences were extracted using SAGE 2000 software.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:The human mixed lineage leukemia 5 (MLL5) protein mediates hematopoietic cell homeostasis, cell cycle and survival, however, the molecular basis underlying MLL5 activities remains unknown. Here, we show that MLL5 is recruited to gene-rich euchromatic regions via the interaction of its PHD finger with the histone mark H3K4me3. The 1.48 Å resolution crystal structure of the MLL5 PHD finger in complex with the H3K4me3 peptide reveals a non-canonical binding mechanism, whereby K4me3 is recognized through a single aromatic residue and an aspartate. The binding induces a His-Asp swapping rearrangement mediated by a C-terminal α-helix. Phosphorylation of H3T3 and H3T6 abrogates the association with H3K4me3 in vitro and in vivo, releasing MLL5 from chromatin in mitosis. This regulatory switch is conserved in the Drosophila ortholog of MLL5, MLL5, and suggests the developmental control for targeting of H3K4me3. Together, our findings provide insight into the molecular basis for the recruitment, exclusion and regulation of MLL5 at chromatin.
Project description:Targeted mouse mutants with inactivated Mixed-Lineage-Leukemia-5 (Mll5, MGI:1924825) alleles exhibit numerical, cell cycle and functional abnormalities in their hematopoietic stem and progenitor cell (HSPC) compartments, including hyper-proliferation of otherwise quiescent hematopoietic stem cells, lack of long-term reconstitution potential and profound radiation sensitivity. Most of the HSPC defects are secondary to increased levels of DNA damage and intracellular accumulation of reactive oxygen species (ROS). To obtain first insights into underlying molecular mechanisms, we performed Affymetrix gene chip analysis using total RNA isolated from FACS-sorted Lin-Sca1+Kit+ (LSK) cells of Mll5+/+ and Mll5-/- mice, both with and without prior long-term treatment with the ROS quencher N-Acetyl-L-Cysteine (NAC). As key finding, microarray data revealed elevated hybridization signals for several transcripts of known or putative IFN-1 target genes in LSK cells from Mll5-/- mice irrespective of NAC-treatment. In fact, comprehensive gene set enrichment analysis identified a number of gene sets closely associated with interferon responses that were significantly affected in Mll5-/- LSK cells. RNA was isolated from FACS-sorted Lin-Sca1+Kit+ (LSK) cells of Mll5+/+ and Mll5-/- mice, both with and without prior long-term treatment with the ROS quencher N-Acetyl-L-Cysteine (NAC)
Project description:The human mixed lineage leukemia 5 (MLL5) protein mediates hematopoietic cell homeostasis, cell cycle and survival, however, the molecular basis underlying MLL5 activities remains unknown. Here, we show that MLL5 is recruited to gene-rich euchromatic regions via the interaction of its PHD finger with the histone mark H3K4me3. The 1.48 à resolution crystal structure of the MLL5 PHD finger in complex with the H3K4me3 peptide reveals a non-canonical binding mechanism, whereby K4me3 is recognized through a single aromatic residue and an aspartate. The binding induces a His-Asp swapping rearrangement mediated by a C-terminal α-helix. Phosphorylation of H3T3 and H3T6 abrogates the association with H3K4me3 in vitro and in vivo, releasing MLL5 from chromatin in mitosis. This regulatory switch is conserved in the Drosophila ortholog of MLL5, MLL5, and suggests the developmental control for targeting of H3K4me3. Together, our findings provide insight into the molecular basis for the recruitment, exclusion and regulation of MLL5 at chromatin. For determaning MLL5 chromatin profile, DamID-MLL5 chromatin profiling was determined in C2C12 cells . Three biological replicates were performed. Normalized data was averaged and HMM approach was applied to establish the bound regions (Straub, T., Grimaud, C., Gilfillan, G. D., Mitterweger, A., and Becker, P. B. (2008). PLoS Genet 4, e1000302)
Project description:Targeted mouse mutants with inactivated Mixed-Lineage-Leukemia-5 (Mll5, MGI:1924825) alleles exhibit numerical, cell cycle and functional abnormalities in their hematopoietic stem and progenitor cell (HSPC) compartments, including hyper-proliferation of otherwise quiescent hematopoietic stem cells, lack of long-term reconstitution potential and profound radiation sensitivity. Most of the HSPC defects are secondary to increased levels of DNA damage and intracellular accumulation of reactive oxygen species (ROS). To obtain first insights into underlying molecular mechanisms, we performed Affymetrix gene chip analysis using total RNA isolated from FACS-sorted Lin-Sca1+Kit+ (LSK) cells of Mll5+/+ and Mll5-/- mice, both with and without prior long-term treatment with the ROS quencher N-Acetyl-L-Cysteine (NAC). As key finding, microarray data revealed elevated hybridization signals for several transcripts of known or putative IFN-1 target genes in LSK cells from Mll5-/- mice irrespective of NAC-treatment. In fact, comprehensive gene set enrichment analysis identified a number of gene sets closely associated with interferon responses that were significantly affected in Mll5-/- LSK cells.