title: Ribosomal RNA Genes in the Protozoan Parasite Leishmania major Possess a Nucleosomal Structure.
abstract: Little is known about nucleosome structure and epigenetic regulation of transcription of rRNA genes in early-branched eukaryotes. Here we analyze the chromatin architecture and distribution of some histone modifications in the rRNA genes in the parasitic protozoon Leishmania major. Southern blots of MNase-partially-digested chromatin with DNA probes spanning the whole rRNA gene repeat showed that the intergenic spacer presents a tight nucleosomal structure, whereas the promoter region is practically devoid of nucleosomes. Intermediate levels of nucleosomes were found in the rRNA coding regions. ChIP assays allowed us to determine that H3K14ac, H3K23ac and H3K27ac, epigenetics marks that are generally associated with activation of transcription, are enriched in the promoter region. In contrast, H4K20me3, which is generally related to transcriptional silencing, was absent from the promoter region and intergenic spacer and enriched in the coding region. Interestingly, the distribution pattern for H3K9me3, generally linked to heterochromatin formation, was very similar to the distribution observed with the euchromatin marks, suggesting that this modification could be involved in transcriptional activation of rRNA genes in L. major.
authors.affiliation: Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. De los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Vizuet-de-Rueda
authors.affiliation: Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. De los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Florencio-Martínez
authors.affiliation: Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. De los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México.
authors.forename: Norma E
authors.initials: NE
authors.lastname: Padilla-Mejía
authors.affiliation: Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, México, D.F., CP 07360, México.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Manning-Cela
authors.affiliation: Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, México, D.F., CP 07360, México.
authors.forename: Rosaura
authors.initials: R
authors.lastname: Hernández-Rivas
authors.affiliation: Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. De los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México. Electronic address: scalv@campus.iztacala.unam.mx.
authors.forename: Santiago
authors.initials: S
authors.lastname: Martínez-Calvillo
mesh_terms: D021901:DNA, Intergenic / Q000235:genetics; D044127:Epigenesis, Genetic / Q000235:genetics; D006570:Heterochromatin / Q000648:ultrastructure*; D006657:Histones / Q000235:genetics; D018320:Leishmania major / Q000235:genetics*; D009707:Nucleosomes / Q000648:ultrastructure*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics / Q000648:ultrastructure*; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: D021901:DNA, Intergenic; D006570:Heterochromatin; D006657:Histones; D009707:Nucleosomes; D012335:RNA, Ribosomal
keywords: Leishmania major; Pol I transcription; epigenetic regulation; histone modification; nucleosome structure.; rRNA genes