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KMID : 0368419920350040415
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Journal of Plant Biology
1992 Volume.35 No. 4 p.415 ~ p.423
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DNA Methylase and Chloroplast DNA Methylation in Chlamydomonas
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金南坤/Kim, Nam Gon
金載潤/李舜熙/李康吾/金榮敏/朴基榮/Kim, Jae Yoon/Lee, Sun Hi/Lee, Kang Oh/Kim, Young Min/Park, Ky Young
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Abstract
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Two kinds of DNA methylases were purified from Chlamydomonas 21 gr(mt^+) gametic cells to determine the DNA methylases related to chloroplast DNA methylation and to examine their affinities for various DNAs. Two DNA methylases had distinct physical properties under the same condition of pH and ionic strength, and had different molecular weights as determined on a nondenatured gradient polyacrylamide gel electrophoresis. As the two enzymes had similar enzymatic activities on λ phage DNA and non-methylated λ DNA, it is suspected that they may act on cytosine methylation. In contrast with DNA methylase Ⅰ, DNA methylase Ⅱ showed a higher methyl-incorporation rate into poly(dG-dC)·poly(dG-dC) than poly(dA-dC)·poly(dG-dT). Therefore, it may have a greater affinity for (G-C) sequence than (A-C). When chloroplast DNA was isolated from Chlamydomonas in the vegetative and gametic stages and the activities of DNA methylase Ⅰ and Ⅱ were examined on these DNAs, they revealed 20% and 10% lower rates, respectively, of methyl-incorporation into the gametic chloroplast DNA than into the vegetative DNA.
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