title: Growth of the protozoan parasite Entamoeba histolytica in 5-azacytidine has limited effects on parasite gene expression.
abstract: BACKGROUND
  In higher eukaryotes DNA methylation regulates important biological functions including silencing of gene expression and protection from adverse effects of retrotransposons. In the protozoan parasite Entamoeba histolytica, a DNA methyltransferase has been identified and treatment with 5-azacytidine (5-AzaC), a potent inhibitor of DNA methyltransferase, has been reported to attenuate parasite virulence. However, the overall extent of DNA methylation and its subsequent effects on global gene expression in this parasite are currently unknown.
  
  
  RESULTS
  In order to identify the genome-wide effects of DNA methylation in E. histolytica, we used a short oligonucleotide microarray representing 9,435 genes (approximately 95% of all annotated amebic genes) and compared the expression profile of E. histolytica HM-1:IMSS parasites with those treated with 23 microM 5-AzaC for up to one week. Overall, 2.1% of genes tested were transcriptionally modulated under these conditions. 68 genes were upregulated and 131 genes down regulated (2-fold change; p-value < 0.05). Sodium-bisulfite treatment and sequencing of genes indicated that there were at least two subsets of genes with genomic DNA methylation in E. histolytica: (i) genes that were endogenously silenced by genomic DNA methylation and for which 5-AzaC treatment induced transcriptional de-repression, and (ii) genes that have genomic DNA methylation, but which were not endogenously silenced by the methylation. We identified among the genes down regulated by 5-AzaC treatment a cysteine proteinase (2.m00545) and lysozyme (52.m00148) both of which have known roles in amebic pathogenesis. Decreased expression of these genes in the 5-AzaC treated E. histolytica may account in part for the parasites reduced cytolytic abilities.
  
  
  CONCLUSIONS
  This work represents the first genome-wide analysis of DNA-methylation in Entamoeba histolytica and indicates that DNA methylation has relatively limited effects on gene expression in this parasite.
authors.affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305-5107, USA. ikmali@stanford.edu <ikmali@stanford.edu>
authors.forename: Ibne Karim M
authors.initials: IK
authors.lastname: Ali
authors.forename: Gretchen M
authors.initials: GM
authors.lastname: Ehrenkaufer
authors.forename: Jason A
authors.initials: JA
authors.lastname: Hackney
authors.forename: Upinder
authors.initials: U
authors.lastname: Singh
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000494:pharmacology*; D016466:CHO Cells; D006224:Cricetinae; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors; D019175:DNA Methylation; D004748:Entamoeba histolytica / Q000187:drug effects* / Q000254:growth & development* / Q000472:pathogenicity; D005786:Gene Expression Regulation / Q000187:drug effects*; D020868:Gene Silencing; D017125:Genes, Protozoan / Q000187:drug effects / Q000502:physiology*; D018503:Genome, Protozoan / Q000502:physiology; D008647:Mesocricetus; D046228:Microarray Analysis; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D014774:Virulence / Q000187:drug effects
chemical_list: D015800:Protozoan Proteins; D004248:DNA (Cytosine-5-)-Methyltransferases; D001374:Azacitidine