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
Chromatin structure is important for controlling gene expression, but mechanisms underlying chromatin remodel- ing are not fully understood. Here we report that an FKBP （FK506 binding protein） type immunophilin, AtF...Chromatin structure is important for controlling gene expression, but mechanisms underlying chromatin remodel- ing are not fully understood. Here we report that an FKBP （FK506 binding protein） type immunophilin, AtFKBP53, possesses histone chaperone activity and is required for repressing ribosomal gene expression in Arabidopsis. The At- FKBP53 protein is a multidomain FKBP with a typical peptidylprolyl isomerase （PPIase） domain and several highly charged domains. Using nucleosome assembly assays, we showed that AtFKBP53 has histone chaperone activity and the charged acidic domains are sufficient for the activity. We show that AtFKBP53 interacts with histone H3 through the acidic domains, whereas the PPIase domain is dispensable for histone chaperone activity or histone binding. Ri- bosomal RNA gene （18S rDNA） is overexpressed when AtFKBP53 activity is reduced or eliminated in Arabidopsis plants. Chromatin immunoprecipitation assay showed that AtFKBP53 is associated with the 18S rDNA gene chro- matin, implicating that AtFKBP53 represses rRNA genes at the chromatin level. This study identifies a new histone chaperone in plants that functions in chromatin remodeling and regulation of transcription.展开更多
AIM： To explore the relationship between acetylation of histone in total chromatin and p21^WAF1 expression regulation in human colorectal carcinoma. METHODS： We analyzed the expression of tumor suppressor gene p21^W...AIM： To explore the relationship between acetylation of histone in total chromatin and p21^WAF1 expression regulation in human colorectal carcinoma. METHODS： We analyzed the expression of tumor suppressor gene p21^WAF1 mRNA by RT-PCR or realtime PCR in 33 samples of colorectal cancerous tissue, corresponding para-cancerous tissue and normal colorectal mucosa, and also examined the level of acetylated histone H3 in total chromatin using Western blotting. RESULTS： The expression level of p21^WAF1 mRNA was significantly lower in colorectal cancerous tissue from 33 patients than in para-cancerous tissue and normal colorectal mucosa （2377.95 ± 865.80 vs 3216.58 ± 1149.42 and 3541.61 ± 1433.17 respectively, P 〈 0.01）. In addition, when p21^WAF1 mRNA expression was undectectable or at very low level （50% less than that in adjacent tissue and normal colorectal mucosa） in all tissues, the level of acetylated histone H3 in colorectal cancerous tissue was significantly lower than that in corresponding para-cancerous tissue and normal colorectal mucosa in five of seven （71.43%） cases. The transcriptional level of p21^WAF1 in colorectal carcinoma might not be associated with its biological behaviors.CONCLUSION： The down-regulation of p21^WAF1 transcription is involved in the tumorigenesis and development of colorectal carcinoma. The down-expression of p21^WAF1 mRNA in colorectal carcinoma might be associated with histone hypoacetylation in chromatin but not with biological behaviors.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We thank Veder Garcia （University of California, Berkeley, USA） for critically reading the paper, Zengyong He for providing the AtFKBP53：：GUS transgenic line and Masami Horikoshi （The University of Tokyo, Japan） for the pET-6His-SpFkbp39P plasmid. This work was supported by grants from the National Science Foundation and US Department of Energy （toSL）.
文摘Chromatin structure is important for controlling gene expression, but mechanisms underlying chromatin remodel- ing are not fully understood. Here we report that an FKBP （FK506 binding protein） type immunophilin, AtFKBP53, possesses histone chaperone activity and is required for repressing ribosomal gene expression in Arabidopsis. The At- FKBP53 protein is a multidomain FKBP with a typical peptidylprolyl isomerase （PPIase） domain and several highly charged domains. Using nucleosome assembly assays, we showed that AtFKBP53 has histone chaperone activity and the charged acidic domains are sufficient for the activity. We show that AtFKBP53 interacts with histone H3 through the acidic domains, whereas the PPIase domain is dispensable for histone chaperone activity or histone binding. Ri- bosomal RNA gene （18S rDNA） is overexpressed when AtFKBP53 activity is reduced or eliminated in Arabidopsis plants. Chromatin immunoprecipitation assay showed that AtFKBP53 is associated with the 18S rDNA gene chro- matin, implicating that AtFKBP53 represses rRNA genes at the chromatin level. This study identifies a new histone chaperone in plants that functions in chromatin remodeling and regulation of transcription.
基金Supported by the Major State Basic Research Development Program of China (973 Program), No. 2005CB522400Shanghai Leading Academic Discipline Project, No. Y0205Shanghai Municipal Commission for Science and Technology to FJY. No.04DZ14006
文摘AIM： To explore the relationship between acetylation of histone in total chromatin and p21^WAF1 expression regulation in human colorectal carcinoma. METHODS： We analyzed the expression of tumor suppressor gene p21^WAF1 mRNA by RT-PCR or realtime PCR in 33 samples of colorectal cancerous tissue, corresponding para-cancerous tissue and normal colorectal mucosa, and also examined the level of acetylated histone H3 in total chromatin using Western blotting. RESULTS： The expression level of p21^WAF1 mRNA was significantly lower in colorectal cancerous tissue from 33 patients than in para-cancerous tissue and normal colorectal mucosa （2377.95 ± 865.80 vs 3216.58 ± 1149.42 and 3541.61 ± 1433.17 respectively, P 〈 0.01）. In addition, when p21^WAF1 mRNA expression was undectectable or at very low level （50% less than that in adjacent tissue and normal colorectal mucosa） in all tissues, the level of acetylated histone H3 in colorectal cancerous tissue was significantly lower than that in corresponding para-cancerous tissue and normal colorectal mucosa in five of seven （71.43%） cases. The transcriptional level of p21^WAF1 in colorectal carcinoma might not be associated with its biological behaviors.CONCLUSION： The down-regulation of p21^WAF1 transcription is involved in the tumorigenesis and development of colorectal carcinoma. The down-expression of p21^WAF1 mRNA in colorectal carcinoma might be associated with histone hypoacetylation in chromatin but not with biological behaviors.
