ABSTRACT
Polyamines are naturally occurring intracellular polycations that are essential for viability and growth of eukaryotes. Dysregulation of polyamine metabolism is a hallmark of cancer and the carcinogenic process, and consequently development of polyamine analogues has emerged as a viable strategy for therapeutic intervention. Previously, we showed that the naturally occurring polyamines spermidine and spermine were quite effective at inducing the oligomerization of nucleosomal arrays in vitro, suggesting that polyamines may play a key role in regulating higher order chromatin structures in vivo. Here, we analyse the ability of a number of synthetic polyamine analogues to potentiate formation of higher order chromatin structures in vitro. We find that a class of long-chain polyamines called oligoamines are potent inducers of nucleosomal array oligomerization in vitro and that these same polyamine analogues rapidly block yeast cell growth.
Subject(s)
Nucleosomes/metabolism , Polyamines/pharmacology , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/growth & development , Cell Proliferation , Molecular Structure , Polyamines/chemistry , Time FactorsABSTRACT
Members of the ATP-dependent family of chromatin remodeling enzymes play key roles in the regulation of transcription, development, DNA repair and cell cycle control. We find that the remodeling activities of the ySWI/SNF, hSWI/SNF, xMi-2 and xACF complexes are nearly abolished by incorporation of linker histones into nucleosomal array substrates. Much of this inhibition is independent of linker histone-induced folding of the arrays. We also find that phosphorylation of the linker histone by Cdc2/Cyclin B kinase can rescue remodeling by ySWI/SNF. These results suggest that linker histones exert a global, genome-wide control over remodeling activities, implicating a new, obligatory coupling between linker histone kinases and ATP-dependent remodeling enzymes.
Subject(s)
Adenosine Triphosphate/metabolism , Chromatin/chemistry , Chromatin/enzymology , Cytidine Deaminase , DNA Helicases , Histones/metabolism , Nucleic Acid Conformation , APOBEC-1 Deaminase , Adenosine Triphosphatases/metabolism , Animals , Autoantigens/metabolism , CDC2 Protein Kinase/metabolism , CDC28 Protein Kinase, S cerevisiae/metabolism , Chromatin/metabolism , Gene Expression Regulation , Humans , Mi-2 Nucleosome Remodeling and Deacetylase Complex , Phosphorylation , RNA-Binding Proteins/metabolism , Transcription Factors/metabolism , Xenopus laevis , YeastsABSTRACT
The SIN domain within histones H3 and H4 is defined by a set of single amino acid substitutions that were initially identified as mutations that alleviate the transcriptional defects associated with inactivation of the SWI/SNF chromatin remodeling complex. Here we use recombinant histones to investigate how Sin- versions of H4 alter the structure of nucleosomal arrays. We find that an R45C substitution within the SIN domain of H4 does not disrupt nucleosome positioning nor does this Sin- version alter the accessibility of nucleosomal DNA. In contrast, we find that the R45C substitution eliminates Mg2+-dependent, intramolecular folding of the nucleosomal arrays. Our results suggest that Sin- versions of histones may alleviate the need for SWI/SNF in vivo by disrupting higher-order chromatin folding.
Subject(s)
Histones/chemistry , Histones/metabolism , Nuclear Proteins , Nucleosomes/chemistry , Nucleosomes/metabolism , Adenosine Triphosphate/metabolism , Amino Acid Substitution , Animals , Chickens , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , DNA, Ribosomal/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Histones/genetics , Magnesium/metabolism , Models, Molecular , Nucleic Acid Conformation/drug effects , Nucleosomes/genetics , Protein Structure, Tertiary/drug effects , RNA, Ribosomal, 5S/genetics , Salts/pharmacology , Sea Urchins/genetics , Templates, Genetic , Transcription Factors/genetics , Transcription Factors/metabolism , Xenopus Proteins/chemistry , Xenopus Proteins/genetics , Xenopus Proteins/metabolism , Xenopus laevisABSTRACT
A new method to prepare Cr(NO)(H(2)O)(5)(2+) from dichromate and NH(2)OH is reported. The chromium nitrosyls Cr(NO)(EHBA)(+) and Cr(NO)(EHBA)(2) (EHBA = 2-ethyl-2-hydoxybutyrate) were prepared by a literature reaction and characterized by continuous wave electron paramagnetic resonance and two-pulse electron spin echo spectroscopy at X-band. The g values are characteristic of a single unpaired electron in a predominantly d(xy)() orbital. In fluid and glassy solutions Cr(NO)(EHBA)(2) is a mixture of cis and trans isomers. Rotation of the methyl groups in the EHBA ligands causes an increased rate of spin echo dephasing at temperatures between 40 and 120 K. For the EHBA complexes echo envelope modulation is observed at temperatures below about 40 K that is attributed to inequivalent coupling to protons of the slowly rotating methyl groups. Both the effect of the methyl rotation on spin echo dephasing and the depth of the proton modulation are dependent on the number of ethyl groups in the ligand, and thus the spin echo experiments provide confirmation of the number of EHBA ligands in the complexes. The spin-lattice relaxation rates for the chromium-nitrosyl complexes at temperatures near 100 K are similar to values reported previously for Cr(V) complexes, which also have a single unpaired electron in a predominantly d(xy)() orbital. For Cr(NO)(H(2)O)(5)(2+), Cr(NO)(EHBA)(+), and Cr(NO)(EHBA)(2) the dominant contribution to spin-lattice relaxation between 12 and 150 K is the Raman process with a Debye temperature, theta(D), of 110-120 K. For Cr(NO)(CN)(5)(3)(-) the data are consistent with a Raman process (theta(D) = 135 K) and a contribution from a local mode, which dominates above about 60 K. The formally low-spin d(5) chromium nitrosyl complexes relax about 5 orders of magnitude more slowly than low-spin d(5) Fe(III) porphyrins, which is attributed to the absence of a low-lying excited state.
