Chromatin boundaries and chromatin domains.
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Animals↗
Biomedical subjects
M Gaszner
Publications and source records attributed to M Gaszner.
Correlation between histone lysine methylation and developmental changes at the chicken beta-globin locus.
Methylation of histones at specific residues plays an important role in transcriptional regulation. Chromatin immunoprecipitation of dimethylated lysine 9 on histone H3 across 53 kilobases of the chicken beta-globin locus during erythropoiesis shows an almost complete anticorrelation between regions of elevated lysine 9 methylation and acetylation. Lysine 9 is methylated most over constitutive condensed chromatin and developmentally inactive globin genes. In contrast, lysine 4 methylation of histone H3 correlates with H3 acetylation. These results lead us to propose a mechanism by which the insulator in the beta-globin locus can protect the globin genes from being silenced by adjacent condensed chromatin.
Acetylation↗
The Zw5 protein, a component of the scs chromatin domain boundary, is able to block enhancer-promoter interaction.
The scs and scs' elements were proposed to function as chromatin domain boundaries for the 87A7 heat shock locus in Drosophila melanogaster. Here we report the identification and characterization of SBP (scs binding protein), a component of the scs nucleoprotein complex. SBP binds specifically to a 24-bp region of scs in vitro and is associated with scs in vivo. Multiple copies of an oligonucleotide containing the SBP recognition sequence are capable of blocking enhancer-promoter interactions in transgene assays. Mutations in the oligonucleotide that disrupt SBP binding in vitro also eliminate enhancer-blocking activity in vivo. We show that SBP is encoded by the zeste-white 5 gene and that mutations in zeste-white 5 reduce the enhancer-blocking activity of the multimerized oligonucleotides.
ATP-Binding Cassette Transporters↗
Spermidine-induced alteration in the gene-spacer discrimination of nucleases in protonated DNA.
The sequence preference of a Drosophila lysosomal DNase was studied on the Drosophila hsp 70 heat-shock and histone recombinants, which carry six different genes, and the surrounding spacer sequences. The distribution of cleavage sites was random in respect of the locations of gene and spacer sequences. However, in the presence of 10 mM spermidine, a major transition was observed: the coding sequences became more susceptible than the spacer regions to nuclease attack. A similar transition was induced in the sequence preference of DNase I if the digestion was performed in the presence of spermidine at pH 5.2. At pH 7.5, spermidine does not influence the sequence preference of DNase I, which indicates the involvement of DNA protonation in this transition. In the presence of spermidine, the distributions of preferred and protected sequences were almost indistinguishable for these nucleases, suggesting that the protonated DNA, and not the enzymes, is the target of spermidine. A Drosophila embryonal protein was detected and partially purified which induced the same transition as observed in the presence of spermidine. The purified protein preferentially protected the spacer DNA sequences against acid DNase or DNase I cleavage in the hsp 70 heat-shock and histone gene recombinants. The protection was concentration dependent and occurred only at pH 5.2. The transition of nuclease specificity is probably due to a conformational change in the protonated DNA, induced by the binding of either the embryonal protein or spermidine.
Animals↗
Genetic and molecular analysis of chromatin domains.
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Animals↗
Purification of a lysosomal DNase from Drosophila melanogaster.
An acid DNase was purified from Drosophila melanogaster till apparent homogeneity by six consecutive chromatographic steps. The enzyme is a lysosomal DNase, because it is glycosylated and carries 1.8-2.4 mol of mannose-6-phosphate/mol of enzyme. The enzyme is fully active without any divalent cation and introduces single stranded nicks into a supercoiled DNA.
Animals↗
The isolated N-terminal DNA binding domain of the c repressor of bacteriophage 16-3 is functional in DNA binding in vivo and in vitro.
The 197 amino acid c repressor of the temperate Rhizobium meliloti phage 16-3 still regulates the OR operator of the phage after removal of its carboxyl terminal region. When cloned in the low-copy-number plasmid pGA46, a severely truncated variant (R1-77), which retains only the first 77 amino acids of the intact protein, repressed in vivo transcription from the phage promoter PR. When the R1-77 repressor was fused to E. coli beta-galactosidase, the hybrid protein bound OR operator DNA in vitro. The behavior of fusion proteins derived from a point mutant is consistent with the assignment of DNA binding specificity to the amino-terminal region. Furthermore two repressor alleles bearing ts mutations that mapped in the R1-77 region (near a helix-turn-helix motif) were also temperature sensitive for regulation of the OR site, while an 18 bp "in frame" deletion mutant, which mapped in the carboxyl terminal segment, regulated the OR operator in wild-type fashion. The carboxyl terminal region of the repressor is however necessary for the control of lysogenic development of 16-3.
Alleles↗