scholarly journals Oncogenic point mutations in the Myb DNA-binding domain alter the DNA-binding properties of Myb at a physiological target gene

2007 ◽  
Vol 35 (21) ◽  
pp. 7237-7247 ◽  
Author(s):  
O. Ivanova ◽  
D. Braas ◽  
K.-H. Klempnauer
Keyword(s):  
Dna Binding ◽  
Target Gene ◽  
Point Mutations ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Binding Properties ◽  
Dna Binding Properties

scholarly journals Overproduction of v-Myc in the nucleus and its excess over Max are not required for avian fibroblast transformation

1993 ◽  
Vol 13 (6) ◽  
pp. 3623-3631
Author(s):  
A T Tikhonenko ◽  
A R Hartman ◽  
M L Linial
Keyword(s):  
Dna Binding ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Point Mutations ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Localization Signal ◽  
Infected Cells ◽  
Fibroblast Transformation

The cellular proto-oncogene c-myc can acquire transforming potential by a number of different means, including retroviral transduction. The transduced allele generally contains point mutations relative to c-myc and is overexpressed in infected cells, usually as a v-Gag-Myc fusion protein. Upon synthesis, v-Gag-Myc enters the nucleus, forms complexes with its heterodimeric partner Max, and in this complex binds to DNA in a sequence-specific manner. To delineate the role for each of these events in fibroblast transformation, we introduced several mutations into the myc gene of the avian retrovirus MC29. We observed that Gag-Myc with a mutated nuclear localization signal is confined predominantly in the cytoplasm and only about 5% of the protein could be detected in the nucleus (less than the amount of endogenous c-Myc). Consequently, only a small fraction of Max is associated with Myc. However, cells infected with this mutant exhibit a completely transformed phenotype in vitro, suggesting that production of enough v-Gag-Myc to tie up all cellular Max is not needed for transformation. While the nuclear localization signal is dispensable for transformation, minimal changes in the v-Gag-Myc DNA-binding domain completely abolish its transforming potential, consistent with a role of Myc as a transcriptional regulator. One of its potential targets might be the endogenous c-myc, which is repressed in wild-type MC29-infected cells. Our experiments with MC29 mutants demonstrate that c-myc down-regulation depends on the integrity of the v-Myc DNA-binding domain and occurs at the RNA level. Hence, it is conceivable that v-Gag-Myc, either directly or circuitously, regulates c-myc transcription.

scholarly journals Molecular and genetic analysis of the toxic effect of RAP1 overexpression in yeast.

Genetics ◽  
1995 ◽  
Vol 141 (4) ◽  
pp. 1253-1262 ◽  
Author(s):  
K Freeman ◽  
M Gwadz ◽  
D Shore
Keyword(s):  
Dna Binding ◽  
Genetic Analysis ◽  
Toxic Effect ◽  
Transcriptional Activation ◽  
Ribosomal Proteins ◽  
Regulatory Protein ◽  
Point Mutations ◽  
Binding Domain ◽  
Dna Binding Domain

Abstract Rap1p is a context-dependent regulatory protein in yeast that functions as a transcriptional activator of many essential genes, including those encoding ribosomal proteins and glycolytic enzymes. Rap1p also participates in transcriptional silencing at HM mating-type loci and telomeres. Overexpression of RAP1 strongly inhibits cell growth, perhaps by interfering with essential transcriptional activation functions within the cell. Here we report a molecular and genetic analysis of the toxic effect of RAP1 overexpression. We show that toxicity does not require the previously defined Rap1p activation and silencing domains, but instead is dependent upon the DNA-binding domain and an adjacent region of unknown function. Point mutations were identified in the DNA-binding domain that relieve the toxic effect of overexpression. Two of these mutations can complement a RAP1 deletion yet cause growth defects and altered DNA-binding properties in vitro. However, a small deletion of the adjacent (downstream) region that abolishes overexpression toxicity has, by itself, no apparent effect on growth or DNA binding. SKO1/ACR1, which encodes a CREB-like repressor protein in yeast, was isolated as a high copy suppressor of the toxicity caused by RAP1 overexpression. Models related to the regulation of Rap1p activity are discussed.

Zinc Binding Properties of the DNA Binding Domain of the 1,25-Dihydroxyvitamin D3Receptor†

Biochemistry ◽  
1997 ◽  
Vol 36 (34) ◽  
pp. 10482-10491 ◽  
Author(s):  
Theodore A. Craig ◽  
Timothy D. Veenstra ◽  
Stephen Naylor ◽  
Andy J. Tomlinson ◽  
Kenneth L. Johnson ◽  
...  
Keyword(s):  
Dna Binding ◽  
Binding Domain ◽  
Zinc Binding ◽  
Dna Binding Domain ◽  
Binding Properties

scholarly journals The Membrane-Bound Transcriptional Regulator CadC Is Activated by Proteolytic Cleavage in Response to Acid Stress

2008 ◽  
Vol 190 (14) ◽  
pp. 5120-5126 ◽  
Author(s):  
Yong Heon Lee ◽  
Ji Hye Kim ◽  
Iel Soo Bang ◽  
Yong Keun Park
Keyword(s):  
Dna Binding ◽  
Target Gene ◽  
Active Form ◽  
Acid Stress ◽  
Transcriptional Regulator ◽  
Binding Domain ◽  
Biologically Active ◽  
Dna Binding Domain ◽  
Inner Membrane ◽  
Bacterial Membranes

ABSTRACT Proteolytic processes often participate in signal transduction across bacterial membranes. In Salmonella enterica serovar Typhimurium, the transcriptional regulator CadC activates genes of lysine decarboxylase system in response to external acidification and exogenous lysine. However, the signaling mechanism of CadC activation remains unexplored. We report here that CadC is located on the inner membrane under normal growth conditions but rapidly cleaved under acid stress conditions, leading to the induction of target gene transcription. As full-length CadC is degraded, the N-terminal fragment containing the DNA-binding domain accumulates in the inner membrane. Moreover, we show that C-terminal truncations of CadC abolish its degradation, resulting in complete loss of activator function. Together, these observations suggest that site-specific proteolysis at the periplasmic domain of CadC generates a biologically active form of N-terminal DNA-binding domain to promote target gene activation.

scholarly journals Overproduction of v-Myc in the nucleus and its excess over Max are not required for avian fibroblast transformation.

1993 ◽  
Vol 13 (6) ◽  
pp. 3623-3631 ◽  
Author(s):  
A T Tikhonenko ◽  
A R Hartman ◽  
M L Linial
Keyword(s):  
Dna Binding ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Point Mutations ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Localization Signal ◽  
Infected Cells ◽  
Fibroblast Transformation

The cellular proto-oncogene c-myc can acquire transforming potential by a number of different means, including retroviral transduction. The transduced allele generally contains point mutations relative to c-myc and is overexpressed in infected cells, usually as a v-Gag-Myc fusion protein. Upon synthesis, v-Gag-Myc enters the nucleus, forms complexes with its heterodimeric partner Max, and in this complex binds to DNA in a sequence-specific manner. To delineate the role for each of these events in fibroblast transformation, we introduced several mutations into the myc gene of the avian retrovirus MC29. We observed that Gag-Myc with a mutated nuclear localization signal is confined predominantly in the cytoplasm and only about 5% of the protein could be detected in the nucleus (less than the amount of endogenous c-Myc). Consequently, only a small fraction of Max is associated with Myc. However, cells infected with this mutant exhibit a completely transformed phenotype in vitro, suggesting that production of enough v-Gag-Myc to tie up all cellular Max is not needed for transformation. While the nuclear localization signal is dispensable for transformation, minimal changes in the v-Gag-Myc DNA-binding domain completely abolish its transforming potential, consistent with a role of Myc as a transcriptional regulator. One of its potential targets might be the endogenous c-myc, which is repressed in wild-type MC29-infected cells. Our experiments with MC29 mutants demonstrate that c-myc down-regulation depends on the integrity of the v-Myc DNA-binding domain and occurs at the RNA level. Hence, it is conceivable that v-Gag-Myc, either directly or circuitously, regulates c-myc transcription.

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