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Selective oxidation of 5-hydroxymethylcytosine with micelle incarcerated oxidants to determine it at single base resolution.

5-Methylcytosine (5mC) is oxidized by ten-eleven translocation (TET) enzymes. This process followed by thymine DNA glycosylase is proposed to be the mechanism for methylcytosine demethylation. 5-Hydroxymethylcytosine (5hmC) is one of the most important key oxidative metabolites in the demethylation process, and therefore, simple and accurate method to determine 5hmC at single base resolution is desired. In the present study, we developed a mild catalytic oxidation of 5-hmC using micelle incarcerated oxidants that enables to determine the position of 5hmC at single base resolution.

The RFTS (replication foci targeting sequence) domain of Dnmt1 is not only necessary for replication-coupled maintenance DNA methylation, but also protects genome from aberrant DNA methylation.

In mammals, DNA methylation plays important roles in embryogenesis and terminal differentiation via regulation of the transcription-competent chromatin state. The methylation patterns are propagated to the next generation during replication by maintenance DNA methyltransferase, Dnmt1, in co-operation with Uhrf1.

Development of a novel method to analyze 5-hydroxymethylcytosine in the CpG sequence of the genome using maintenance DNA methyltransferase, DNMT1.

In mammals, cytosine in the CpG sequence is often methylated by DNA methyltransferase (Dnmt). Methylated cytosine (5mC) plays crucial roles in gene silencing, genomic imprinting, X-chromosome inactivation and the stability of genomic DNA. Aberrant DNA methylation causes embryonic lethality and cancer. Recently, 5-hydoxymethylcytosine (5hmC) was discovered to be a new modification of cytosine, being an intermediate of the demethylation process, and thus is implicated in the pluripotency of stem cells, development, and disease. Therefore, it is quite important to develop the technique to analyze the position of 5hmC in genome. To determine 5hmC at single-base resolution, several techniques have been reported. However, each method has advantages and disadvantages.

Nucleosome compaction facilitates HP1γ binding to methylated H3K9.

The α, β and γ isoforms of mammalian heterochromatin protein 1 (HP1) selectively bind to methylated lysine 9 of histone H3 via their chromodomains. Although the phenotypes of HP1-knockout mice are distinct for each isoform, the molecular mechanisms underlying HP1 isoform-specific function remain elusive. In the present study, we found that in contrast to HP1α, HP1γ could not bind tri-methylated H3 lysine 9 in a reconstituted tetra-nucleosomes when the nucleosomes were in an uncompacted state. The hinge region connecting HP1’s chromodomain and chromoshadow domain contributed to the distinct recognition of the nucleosomes by HP1α and HP1γ.

Synthesis of histone proteins by CPE ligation using a recombinant peptide as the C-terminal building block.

The post-translational modification of histones plays an important role in gene expression. We report herein on a method for synthesizing such modified histones by ligating chemically prepared N-terminal peptides and C-terminal recombinant peptide building blocks. Based on their chemical synthesis, core histones can be categorized as two types; histones H2A, H2B and H4 which contain no Cys residues, and histone H3 which contains a Cys residue(s) in the C-terminal region. A combination of native chemical ligation and desulphurization can be simply used to prepare histones without Cys residues. For the synthesis of histone H3, the endogenous Cys residue(s) must be selectively protected, while keeping the N-terminal Cys residue of the C-terminal building block that is introduced for purposes of chemical ligation unprotected.

Chemical Synthesis of O-Glycosylated Human Interleukin-2 by the Reverse Polarity Protection Strategy.

 The chemical synthesis of human interleukin-2 (IL-2) , having a core 1 sugar, by a ligation method is reported. Although IL-2 is a globular glycoprotein, its C-terminal region, in particular (99-133), is extremely insoluble when synthesized by solid-phase method. To overcome this problem, the side-chain carboxylic acid of the Glu residues was protected by a picolyl ester, thus reversing its polarity from negative to positive. This reverse polarity protection significantly increased the isoelectric point of the peptide segment and made it positive under acidic conditions and facilitated the purification. An efficient method to prepare the prolyl peptide thioester required for the synthesis of the (28-65) segment was also developed. These efforts resulted in the total synthesis of the glycosylated IL-2 having full biological activity.