Dimethylation of histone H3 lysine 9 （H3K9me2） is an important epigenetic mark associated with transcription repression. Here, we identified PHF8, a JmjC-domain-containing protein, as a histone demethylase specific ...Dimethylation of histone H3 lysine 9 （H3K9me2） is an important epigenetic mark associated with transcription repression. Here, we identified PHF8, a JmjC-domain-containing protein, as a histone demethylase specific for this repressing mark. Recombinant full-length wild type protein could remove methylation from H3K9me2, but mutation of a conserved histidine to alanine H247A abolished the demethylase activity. Overexpressed exogenous PHF8 was colocalized with B23 staining. Endogenous PHF8 was also colocalized with B23 and fibrillarin, two well-established nucleolus proteins, suggesting that PHF8 is localized in the nucleolus and may regulate rRNA transcription. Indeed, PHF8 bound to the promoter region of the rDNA gene. Knockdown of PHF8 reduced the expression of rRNA, and overexpression of the gene resulted in upregulation of rRNA transcript. Concomitantly, H3K9me2 level was elevated in the promoter region of the rDNA gene in PHF8 knockdown cells and reduced significantly when the wild type but not the catalytically inactive H247A mutant PHF8 was overexpressed. Thus, our study identified a histone demethylase for H3K9me2 that regulates rRNA transcription.展开更多
Mercury-resistant strain D2 was isolated from mercury-contaminated soil and investigations on its 16S rDNA sequence,growth,minimal inhibitory concentrations(MICs) of metals,antibiotic susceptibility and mer gene were ...Mercury-resistant strain D2 was isolated from mercury-contaminated soil and investigations on its 16S rDNA sequence,growth,minimal inhibitory concentrations(MICs) of metals,antibiotic susceptibility and mer gene were conducted.The strain D2 can grow in the medium containing 60 mg/L mercury ion.It presents more than 99% identity of 16S rRNA gene with Pseudomonas aeruginosa,and exhibits high MIC values for heavy metals and a large spectrum antibiotics resistance.The mer RT gene sequence was amplified from chromosome.Strain D2 is identified as Pseudomonas aeruginosa and the resistance to mercuric ion is related to chromosome.展开更多
基金Acknowledgments We thank the cell biology core facility for confocal study. The PHF8 antibody was kindly provided by Dr Jiemin Wong （East China Normal University）. This work was supported by the National Basic Research Program of China （2007CB947900, 2010CB529705, 2007CB947100）, the Chinese Academy of Sci- ences （KSCX2-YW-R-04, KSCX2-YW-R-I 11）, the National Natural Science Foundation of China （30870538, 90919026）, Postdoctoral fellowship （20090460670）, and the Council of Shanghai Municipal Government for Science and Technology.
文摘Dimethylation of histone H3 lysine 9 （H3K9me2） is an important epigenetic mark associated with transcription repression. Here, we identified PHF8, a JmjC-domain-containing protein, as a histone demethylase specific for this repressing mark. Recombinant full-length wild type protein could remove methylation from H3K9me2, but mutation of a conserved histidine to alanine H247A abolished the demethylase activity. Overexpressed exogenous PHF8 was colocalized with B23 staining. Endogenous PHF8 was also colocalized with B23 and fibrillarin, two well-established nucleolus proteins, suggesting that PHF8 is localized in the nucleolus and may regulate rRNA transcription. Indeed, PHF8 bound to the promoter region of the rDNA gene. Knockdown of PHF8 reduced the expression of rRNA, and overexpression of the gene resulted in upregulation of rRNA transcript. Concomitantly, H3K9me2 level was elevated in the promoter region of the rDNA gene in PHF8 knockdown cells and reduced significantly when the wild type but not the catalytically inactive H247A mutant PHF8 was overexpressed. Thus, our study identified a histone demethylase for H3K9me2 that regulates rRNA transcription.
基金Project(50621063) supported by the National Natural Science Foundation of ChinaProject(2004CB619204) supported by the National Basic Research Program of ChinaProject(2009sk3035) supported by the Science and Technology Program of Hunan Province,China
文摘Mercury-resistant strain D2 was isolated from mercury-contaminated soil and investigations on its 16S rDNA sequence,growth,minimal inhibitory concentrations(MICs) of metals,antibiotic susceptibility and mer gene were conducted.The strain D2 can grow in the medium containing 60 mg/L mercury ion.It presents more than 99% identity of 16S rRNA gene with Pseudomonas aeruginosa,and exhibits high MIC values for heavy metals and a large spectrum antibiotics resistance.The mer RT gene sequence was amplified from chromosome.Strain D2 is identified as Pseudomonas aeruginosa and the resistance to mercuric ion is related to chromosome.
文摘游仆类是纤毛虫中进化最为复杂和高等的一大类群,为了进一步探索和完善游仆类的多样性,本研究利用活体观察、蛋白银和银浸法染色技术对采自青岛小西湖的小腔游仆虫(Euplotes aediculatus)的形态学及细胞发生学进行了详尽的研究,并在完整的形态学及发生学研究基础上,测定了小腔游仆虫的核糖体小亚基基因(SSU r DNA)序列,通过序列比较和分子系统树构建等方法,对小腔游仆虫的系统地位进行了分析。结果表明:本种鉴别特征为9根额腹棘毛,5根横棘毛,2根缘棘毛,2根尾棘毛,8列背触毛,double-eurystomus型银线系。发生学特征包括:(1)后仔虫口原基在表皮下独立发生,前仔虫完全继承老口围带;(2)额–腹–横棘毛原基从左向右按照3:3:3:2:2的模式形成额腹棘毛和横棘毛;(3)前后仔虫最左侧额腹棘毛分别由独立产生的原基形成;(4)缘棘毛原基独立发生;(5)初级背触毛原基来自虫体中部老结构的反分化;(6)前后仔虫尾棘毛分别来自最右侧2列背触毛原基和老背触毛列末端;这些特征显示出游仆虫属个体发生模式的高度保守性。分子系统分析与形态学数据一致,即游仆虫属为单元发生,且小腔游仆虫与艾美游仆虫(Euplotes amieti)、阔口游仆虫(E.eurystomus)和伍氏游仆虫(E.woodruffi)聚在一起。
