Research Project
Grant-in-Aid for Scientific Research (C)
The goal of this study was to clarify the regulatory mechanisms of proplatelet formation through analyang the function of small Maf proteins in megakaryocyte differentiation and maturation and identifying the target genes regulated downstream of small Maf.(1)Structure-function analysis of small Maf in megakaryocytesDimeric transcription factors often consist of one ubiquitous subunit complexed with a more highly restricted partner molecule. MafG is a more common subunit of the MafG:p45 heterodimer, which is an indispensable transcriptional activator mediating proplatelet formation in megakaryocytes. Excess MafG antagonizes the activity of the MafG:p45 heterodimer by forming an inhibitory homodimer, thereby blocking proplatelet formation ; thus MafG both activates and represses transcription depending on its relative abundance. Here we report that MafG is conjugated to SUMO-2/3 in vivo and that SUMOylation-defective MafG, when expressed in megakaryocytes, participates normally in transc … More riptional activation, but not in repression. While MafG was found in both heterochromatin and euchromatin, the mutant MafG failed to be localized in heterochromatin. We conclude that SUMOylation is required for MafG-mediated repression and localization to heterochromatin, and thus SUMOylation of the broadly expressed component of this dimeric transcription factor determines one aspect of its transcriptional potential.(2)Identification of a novel gene regulated downstream of small Maf in megakaryocytes.In order to clarify the molecular mechanisms operating in the process of proplatelet formation, we searched for the differentially expressed genes between the wild type and small maf mutant megakaryocytes. Among various factors relating to the cytoskeleton, one novel factor called clone 325 was isolated through the subtraction screening. The full length cDNA was obtained from the brain cDNA library, and the deduced amino acid sequence revealed one leucine zipper-like motif but no canonical functional motifs. The clone 325 was highly expressed in the primary megakaryocytes purified from the bone marrow, but its abundance was relatively low in immature hematopoietic cells and in erythroid cells. We disrupted the gene of the clone 325 in mouse and found that the homozygous animals are viable and displayed no abnormality in the cell counts of the peripheral blood. But when megakaryocytes from the bone marrow of the mutant animals were observed, we found that very few cells properly protruded normal proplatelets. This result suggests that the clone 325 is important for the proplatelet formation. Less
All 2005 2004 2003 Other
All Journal Article (29 results) Publications (8 results)
J Biol Chem. 280(6)
Pages: 4483-4490
J.Biol.Chem. 280
Trends Mol Med. 10(11)
Pages: 549-557
Biochem Biophys Res Commun. 321(1)
Pages: 72-79
Proc Natl Acad Sci USA. 101(17)
Pages: 6379-6384
J Biol Chem. 279(24)
Pages: 25204-25210
Genes Cells. 9(2)
Pages: 153-164
Genes Cells 9
J.Biol.Chem. 279
Proc.Natl.Acad.Sci.USA 101
Biochem.Biophys.Res.Commun. 321
Trends Mol.Med. 10
Proc Natl Acad Sci U S A. 101(17)
生化学 75(9)
Pages: 1193-1201
10011724682
Nat Genet. 35(3)
Pages: 238-245
Blood 102(10)
Pages: 3575-3583
Proc Natl Acad Sci USA. 100(10)
Pages: 5652-5657
Biochem Biophys Res Commun 303(1)
Pages: 105-111
Mol Cell Biol 23(4)
Pages: 1163-1174
J Biol Chem 278(10)
Pages: 8135-8145
J.Biol.Chem. 278
Mol.Cell.Biol. 23
Biochem.Biophys.Res.Commun. 303
Proc.Natl.Acad.Sci.USA 100
Blood 102
Nat.Genet. 35
Proc Natl Acad Sci U S A. 100(10)
J Biol Chem. 278(10)
