scholarly journals MyoD regulates apoptosis of myoblasts through microRNA-mediated down-regulation of Pax3

2010 ◽  
Vol 191 (2) ◽  
pp. 347-365 ◽  
Author(s):  
Hiroyuki Hirai ◽  
Mayank Verma ◽  
Shuichi Watanabe ◽  
Christopher Tastad ◽  
Yoko Asakura ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Untranslated Region ◽  
Terminal Differentiation ◽  
Wild Type ◽  
Down Regulation ◽  
Muscle Stem Cells ◽  
Myod Gene ◽  
Myod Expression

The molecules that regulate the apoptosis cascade are also involved in differentiation and syncytial fusion in skeletal muscle. MyoD is a myogenic transcription factor that plays essential roles in muscle differentiation. We noticed that MyoD−/− myoblasts display remarkable resistance to apoptosis by down-regulation of miR-1 (microRNA-1) and miR-206 and by up-regulation of Pax3. This resulted in transcriptional activation of antiapoptotic factors Bcl-2 and Bcl-xL. Forced MyoD expression induces up-regulation of miR-1 and miR-206 and down-regulation of Pax3, Bcl-2, and Bcl-xL along with increased apoptosis in MyoD−/− myoblasts. In contrast, MyoD gene knockdown increases cell survival of wild-type myoblasts. The 3′ untranslated region of Pax3 mRNA contains two conserved miR-1/miR-206–binding sites, which are required for targeting of these microRNAs (miRNAs). Therefore, these data suggest that MyoD not only regulates terminal differentiation but also apoptosis through miRNA-mediated down-regulation of Pax3. Finally, MyoD, miR-1, and miR-206 are all down-regulated in quiescent satellite cells, which may be required for maintenance of muscle stem cells.

DNA-binding and transcriptional regulatory properties of hepatic leukemia factor (HLF) and the t(17;19) acute lymphoblastic leukemia chimera E2A-HLF

1994 ◽  
Vol 14 (9) ◽  
pp. 5986-5996
Author(s):  
S P Hunger ◽  
R Brown ◽  
M L Cleary
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Lymphoblastic Leukemia ◽  
Consensus Sequence ◽  
Reporter Genes ◽  
Wild Type ◽  
Basic Leucine Zipper

The t(17;19) translocation in acute lymphoblastic leukemias results in creation of E2A-hepatic leukemia factor (HLF) chimeric proteins that contain the DNA-binding and protein dimerization domains of the basic leucine zipper (bZIP) protein HLF fused to a portion of E2A proteins with transcriptional activation properties. An in vitro binding site selection procedure was used to determine DNA sequences preferentially bound by wild-type HLF and chimeric E2A-HLF proteins isolated from various t(17;19)-bearing leukemias. All were found to selectively bind the consensus sequence 5'-GTTACGTAAT-3' with high affinity. Wild-type and chimeric HLF proteins also bound closely related sites identified previously for bZIP proteins of both the proline- and acidic amino acid-rich (PAR) and C/EBP subfamilies; however, E2A-HLF proteins were significantly less tolerant of certain deviations from the HLF consensus binding site. These differences were directly attributable to loss of an HLF ancillary DNA-binding domain in all E2A-HLF chimeras and were further exacerbated by a zipper mutation in one isolate. Both wild-type and chimeric HLF proteins displayed transcriptional activator properties in lymphoid and nonlymphoid cells on reporter genes containing HLF or C/EBP consensus binding sites. But on reporter genes with nonoptimal binding sites, their transcriptional properties diverged and E2A-HLF competitively inhibited activation by wild-type PAR proteins. These findings establish a spectrum of binding site-specific transcriptional properties for E2A-HLF which may preferentially activate expression of select subordinate genes as a homodimer and potentially antagonize expression of others through heteromeric interactions.

scholarly journals Dissection of a carboxy-terminal region of the yeast regulatory protein RAP1 with effects on both transcriptional activation and silencing

1992 ◽  
Vol 12 (3) ◽  
pp. 1209-1217
Author(s):  
C F Hardy ◽  
D Balderes ◽  
D Shore
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Binding Protein ◽  
Binding Domain ◽  
Dominant Negative Effect ◽  
Dna Binding Domain ◽  
Wild Type ◽  
Carboxy Terminal

RAP1 is an essential sequence-specific DNA-binding protein in Saccharomyces cerevisiae whose binding sites are found in a large number of promoters, where they function as upstream activation sites, and at the silencer elements of the HMR and HML mating-type loci, where they are important for repression. We have examined the involvement of specific regions of the RAP1 protein in both repression and activation of transcription by studying the properties of a series of hybrid proteins containing RAP1 sequences fused to the DNA-binding domain of the yeast protein GAL4 (amino acids 1 to 147). GAL4 DNA-binding domain/RAP1 hybrids containing only the carboxy-terminal third of the RAP1 protein (which lacks the RAP1 DNA-binding domain) function as transcriptional activators of a reporter gene containing upstream GAL4 binding sites. Expression of some hybrids from the strong ADH1 promoter on multicopy plasmids has a dominant negative effect on silencers, leading to either partial or complete derepression of normally silenced genes. The GAL4/RAP1 hybrids have different effects on wild-type and several mutated but functional silencers. Silencers lacking either an autonomously replicating sequence consensus element or the RAP1 binding site are strongly derepressed, whereas the wild-type silencer or a silencer containing a deletion of the binding site for another silencer-binding protein, ABF1, are only weakly affected by hybrid expression. By examining a series of GAL4 DNA-binding domain/RAP1 hybrids, we have mapped the transcriptional activation and derepression functions to specific parts of the RAP1 carboxy terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals DNA-binding and transcriptional regulatory properties of hepatic leukemia factor (HLF) and the t(17;19) acute lymphoblastic leukemia chimera E2A-HLF.

1994 ◽  
Vol 14 (9) ◽  
pp. 5986-5996 ◽  
Author(s):  
S P Hunger ◽  
R Brown ◽  
M L Cleary
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Lymphoblastic Leukemia ◽  
Consensus Sequence ◽  
Reporter Genes ◽  
Wild Type ◽  
Basic Leucine Zipper

The t(17;19) translocation in acute lymphoblastic leukemias results in creation of E2A-hepatic leukemia factor (HLF) chimeric proteins that contain the DNA-binding and protein dimerization domains of the basic leucine zipper (bZIP) protein HLF fused to a portion of E2A proteins with transcriptional activation properties. An in vitro binding site selection procedure was used to determine DNA sequences preferentially bound by wild-type HLF and chimeric E2A-HLF proteins isolated from various t(17;19)-bearing leukemias. All were found to selectively bind the consensus sequence 5'-GTTACGTAAT-3' with high affinity. Wild-type and chimeric HLF proteins also bound closely related sites identified previously for bZIP proteins of both the proline- and acidic amino acid-rich (PAR) and C/EBP subfamilies; however, E2A-HLF proteins were significantly less tolerant of certain deviations from the HLF consensus binding site. These differences were directly attributable to loss of an HLF ancillary DNA-binding domain in all E2A-HLF chimeras and were further exacerbated by a zipper mutation in one isolate. Both wild-type and chimeric HLF proteins displayed transcriptional activator properties in lymphoid and nonlymphoid cells on reporter genes containing HLF or C/EBP consensus binding sites. But on reporter genes with nonoptimal binding sites, their transcriptional properties diverged and E2A-HLF competitively inhibited activation by wild-type PAR proteins. These findings establish a spectrum of binding site-specific transcriptional properties for E2A-HLF which may preferentially activate expression of select subordinate genes as a homodimer and potentially antagonize expression of others through heteromeric interactions.

scholarly journals Regulation of angiogenesis through a microRNA (miR-130a) that down-regulates antiangiogenic homeobox genes GAX and HOXA5

Blood ◽  
2008 ◽  
Vol 111 (3) ◽  
pp. 1217-1226 ◽  
Author(s):  
Yun Chen ◽  
David H. Gorski
Keyword(s):  
Binding Sites ◽  
Untranslated Region ◽  
Vascular Endothelial Cells ◽  
Homeobox Gene ◽  
Vascular Endothelial ◽  
Down Regulation ◽  
Antiangiogenic Activity ◽  
Genome Wide ◽  
A Genome ◽  
Genome Wide Search

Abstract Angiogenesis is critical to tumor progression. The homeobox gene GAX inhibits angiogenesis in vascular endothelial cells (ECs). We have identified a microRNA (miR-130a) that regulates GAX expression and hypothesized that it plays a major role in modulating GAX activity in ECs. A 280-bp fragment from the GAX 3′-untranslated region (3′-UTR) containing 2 miR-130a targeting sites was observed to be required for the rapid down-regulation of GAX expression by serum and proangiogenic factors, whereas the activity of the GAX promoter did not vary with exposure to serum or proangiogenic factors. This same 280-bp sequence in the GAX 3′-UTR cloned into the psiCHECK2-Luciferase vector mediated serum-induced down-regulation of the reporter gene when placed 3′ of it. Finally, forced expression of miR-130a inhibits GAX expression through this specific GAX 3′-UTR sequence. A genome-wide search for other possible miR-130a binding sites revealed an miR-130a targeting site in the 3′-UTR of the antiangiogenic homeobox gene HOXA5, the expression and antiangiogenic activity of which are also inhibited by miR-130a. From these data, we conclude that miR-130a is a regulator of the angiogenic phenotype of vascular ECs largely through its ability to modulate the expression of GAX and HOXA5.

Cell heterogeneity upon myogenic differentiation: down-regulation of MyoD and Myf-5 generates ‘reserve cells’

1998 ◽  
Vol 111 (6) ◽  
pp. 769-779 ◽  
Author(s):  
N. Yoshida ◽  
S. Yoshida ◽  
K. Koishi ◽  
K. Masuda ◽  
Y. Nabeshima
Keyword(s):  
Cell Cycle ◽  
Myogenic Differentiation ◽  
Significant Proportion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Growth Conditions ◽  
Down Regulation ◽  
Undifferentiated Cells ◽  
Myoblast Cells ◽  
Myod Expression

When a proliferating myoblast culture is induced to differentiate by deprivation of serum in the medium, a significant proportion of cells escape from terminal differentiation, while the rest of the cells differentiate. Using C2C12 mouse myoblast cells, this heterogeneity observed upon differentiation was investigated with an emphasis on the myogenic regulatory factors. The differentiating part of the cell population followed a series of well-described events, including expression of myogenin, p21(WAF1), and contractile proteins, permanent withdrawal from the cell cycle and cell fusion, whereas the rest of the cells did not initiate any of these events. Interestingly, the latter cells showed an undetectable or greatly reduced level of MyoD and Myf-5 expression, which had been originally expressed in the undifferentiated proliferating myoblasts. When these undifferentiated cells were isolated and returned to the growth conditions, they progressed through the cell cycle and regained MyoD expression. These cells demonstrated identical features with the original culture on the deprivation of serum. They produced both MyoD-positive differentiating and MyoD-negative undifferentiated populations once again. Thus the undifferentiated cells in the serum-deprived culture were designated ‘reserve cells’. Upon serum deprivation, MyoD expression rapidly decreased as a result of down-regulation in approximately 50% of the cells. After this heterogenization, MyoD positive cells expressed myogenin, which is the earliest known event of terminal differentiation and marks irreversible commitment to this, while MyoD-negative cells did not differentiate and became the reserve cells. We also demonstrated that ectopic expression of MyoD converted the reserve cells to differentiating cells, indicating that down-regulation of MyoD is a causal event in the formation of reserve cells.

scholarly journals Transformation properties of the E2a-Pbx1 chimeric oncoprotein: fusion with E2a is essential, but the Pbx1 homeodomain is dispensable.

1994 ◽  
Vol 14 (12) ◽  
pp. 8304-8314 ◽  
Author(s):  
K Monica ◽  
D P LeBrun ◽  
D A Dedera ◽  
R Brown ◽  
M L Cleary
Keyword(s):  
Transcriptional Activation ◽  
Binding Sites ◽  
Chromosomal Translocation ◽  
Wild Type ◽  
3T3 Cells ◽  
Homeodomain Proteins ◽  
Malignant Lymphomas ◽  
Oncogenic Potential ◽  
Related Proteins ◽  
Nih 3T3

The t(1;19) chromosomal translocation in acute lymphoblastic leukemias creates chimeric E2a-Pbx1 oncoproteins that can act as DNA-binding activators of transcription. A structural analysis of the functional domains of E2a-Pbx1 showed that portions of both E2a and Pbx1 were essential for transformation of NIH 3T3 cells and transcriptional activation of synthetic reporter genes containing PBX1 consensus binding sites. Hyperexpression of wild-type or experimentally truncated Pbx1 proteins was insufficient for transformation, consistent with their inability to activate transcription. When fused with E2a, the Pbx-related proteins Pbx2 and Pbx3 were also transformation competent, demonstrating that all known members of this highly similar subfamily of homeodomain proteins have latent oncogenic potential. The oncogenic contributions of E2a to the chimeras were localized to transactivation motifs AD1 and AD2, as their mutation significantly impaired transformation. Either the homeodomain or Pbx1 amino acids flanking this region could mediate transformation when fused to E2a. However, the homeodomain was not essential for transformation, since a mutant E2a-Pbx1 protein (E2a-Pbx delta HD) lacking the homeodomain efficiently transformed fibroblasts and induced malignant lymphomas in transgenic mice. Thus, transformation mediated by the chimeric oncoprotein E2a-Pbx1 is absolutely dependent on motifs acquired from E2a but the Pbx1 homeodomain is optional. The latter finding suggests that E2a-Pbx1 may interact with cellular proteins that assist or mediate alterations in gene expression responsible for oncogenesis even in the absence of homeodomain-DNA interactions.

scholarly journals Dissection of a carboxy-terminal region of the yeast regulatory protein RAP1 with effects on both transcriptional activation and silencing.

1992 ◽  
Vol 12 (3) ◽  
pp. 1209-1217 ◽  
Author(s):  
C F Hardy ◽  
D Balderes ◽  
D Shore
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Binding Protein ◽  
Binding Domain ◽  
Dominant Negative Effect ◽  
Dna Binding Domain ◽  
Wild Type ◽  
Carboxy Terminal

RAP1 is an essential sequence-specific DNA-binding protein in Saccharomyces cerevisiae whose binding sites are found in a large number of promoters, where they function as upstream activation sites, and at the silencer elements of the HMR and HML mating-type loci, where they are important for repression. We have examined the involvement of specific regions of the RAP1 protein in both repression and activation of transcription by studying the properties of a series of hybrid proteins containing RAP1 sequences fused to the DNA-binding domain of the yeast protein GAL4 (amino acids 1 to 147). GAL4 DNA-binding domain/RAP1 hybrids containing only the carboxy-terminal third of the RAP1 protein (which lacks the RAP1 DNA-binding domain) function as transcriptional activators of a reporter gene containing upstream GAL4 binding sites. Expression of some hybrids from the strong ADH1 promoter on multicopy plasmids has a dominant negative effect on silencers, leading to either partial or complete derepression of normally silenced genes. The GAL4/RAP1 hybrids have different effects on wild-type and several mutated but functional silencers. Silencers lacking either an autonomously replicating sequence consensus element or the RAP1 binding site are strongly derepressed, whereas the wild-type silencer or a silencer containing a deletion of the binding site for another silencer-binding protein, ABF1, are only weakly affected by hybrid expression. By examining a series of GAL4 DNA-binding domain/RAP1 hybrids, we have mapped the transcriptional activation and derepression functions to specific parts of the RAP1 carboxy terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

MyoD expression marks the onset of skeletal myogenesis in Myf-5 mutant mice

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3083-3092 ◽  
Author(s):  
T. Braun ◽  
E. Bober ◽  
M.A. Rudnicki ◽  
R. Jaenisch ◽  
H.H. Arnold
Keyword(s):  
Developmental Time ◽  
Contractile Proteins ◽  
Precursor Cells ◽  
Mutant Mice ◽  
Wild Type ◽  
Myogenic Factor ◽  
Myod Gene ◽  
Muscle Precursor Cells ◽  
Myod Expression

The expression pattern of myogenic regulatory factors and myotome-specific contractile proteins was studied during embryonic development of Myf-5 mutant mice by in situ hybridization and immunohistochemistry. In contrast to somites in wild-type embryos, no expression of myogenin and Myf-6 (MRF4), or any other myotomal markers was detected in mutant animals at E9.0 and E10.0 indicating that Myf-5 plays a crucial role during this developmental period. Significantly, the onset of MyoD expression in rostral somites of E10.5 embryos was unaffected by the Myf-5 mutation suggesting that the activation of the MyoD gene occurs independently of Myf-5 at the correct developmental time. Immediately after the activation of MyoD myogenin transcripts and protein accumulated within the myotome. The first contractile proteins of the sarcomeric apparatus appeared slightly later. By E11.5 the expression of muscle markers were indistinguishable between wild-type and Myf-5 mutant mice. The migration of muscle precursor cells that leave the somites to form limb musculature was monitored in Myf-5-mutant mice by Pax-3 expression. Pax-3-positive cells were equally found in somites and limbs of E10.0 wild-type and mutant mice indicating that myogenic factor expression at the level of somites is not a prerequisite for determination and subsequent migration of limb precursor cells.

Transformation properties of the E2a-Pbx1 chimeric oncoprotein: fusion with E2a is essential, but the Pbx1 homeodomain is dispensable

1994 ◽  
Vol 14 (12) ◽  
pp. 8304-8314
Author(s):  
K Monica ◽  
D P LeBrun ◽  
D A Dedera ◽  
R Brown ◽  
M L Cleary
Keyword(s):  
Transcriptional Activation ◽  
Binding Sites ◽  
Chromosomal Translocation ◽  
Wild Type ◽  
3T3 Cells ◽  
Homeodomain Proteins ◽  
Malignant Lymphomas ◽  
Oncogenic Potential ◽  
Related Proteins ◽  
Nih 3T3

The t(1;19) chromosomal translocation in acute lymphoblastic leukemias creates chimeric E2a-Pbx1 oncoproteins that can act as DNA-binding activators of transcription. A structural analysis of the functional domains of E2a-Pbx1 showed that portions of both E2a and Pbx1 were essential for transformation of NIH 3T3 cells and transcriptional activation of synthetic reporter genes containing PBX1 consensus binding sites. Hyperexpression of wild-type or experimentally truncated Pbx1 proteins was insufficient for transformation, consistent with their inability to activate transcription. When fused with E2a, the Pbx-related proteins Pbx2 and Pbx3 were also transformation competent, demonstrating that all known members of this highly similar subfamily of homeodomain proteins have latent oncogenic potential. The oncogenic contributions of E2a to the chimeras were localized to transactivation motifs AD1 and AD2, as their mutation significantly impaired transformation. Either the homeodomain or Pbx1 amino acids flanking this region could mediate transformation when fused to E2a. However, the homeodomain was not essential for transformation, since a mutant E2a-Pbx1 protein (E2a-Pbx delta HD) lacking the homeodomain efficiently transformed fibroblasts and induced malignant lymphomas in transgenic mice. Thus, transformation mediated by the chimeric oncoprotein E2a-Pbx1 is absolutely dependent on motifs acquired from E2a but the Pbx1 homeodomain is optional. The latter finding suggests that E2a-Pbx1 may interact with cellular proteins that assist or mediate alterations in gene expression responsible for oncogenesis even in the absence of homeodomain-DNA interactions.

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