title: Trafficking and chromatin dynamics of holocarboxylase synthetase during development of Drosophila melanogaster.
abstract: This work examines the cellular localization of holocarboxylase synthetase (HCS) and its association to chromatin during different stages of development of Drosophila melanogaster. While HCS is well known for its role in the attachment of biotin to biotin-dependent carboxylase, it also regulates the transcription of HCS and carboxylases genes by triggering a cGMP-dependent signal transduction cascade. Further, its presence in the nucleus of cells suggests additional regulatory roles, but the mechanism involved has remained elusive. In this study, we show in D. melanogaster that HCS migrates to the nucleus at the gastrulation stage. In polytene chromosomes, it is associated to heterochromatin bands where it co-localizes with histone 3 trimethylated at lysine 9 (H3K9met3) but not with the euchromatin mark histone 3 acetylated at lysine 9 (H3K9ac). Further, we demonstrate the association of HCS with the hsp70 promoter by immunofluorescence and chromatin immuno-precipitation (ChIP) of associated DNA sequences. We demonstrate the occupancy of HCS to the core promoter region of the transcriptionally inactive hsp70 gene. On heat-shock activation of the hsp70 promoter, HCS is displaced and the promoter region becomes enriched with the TFIIH subunits XPD and XPB and elongating RNA pol II, the latter also demonstrated using ChIP assays. We suggest that HCS may have a role in the repression of gene expression through a mechanism involving its trafficking to the nucleus and interaction with heterochromatic sites coincident with H3K9met3.
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México DF 04510, Mexico. sandraquel@biomedicas.unam.mx
authors.forename: Sandra
authors.initials: S
authors.lastname: Reyes-Carmona
authors.forename: Viviana
authors.initials: V
authors.lastname: Valadéz-Graham
authors.forename: Javier
authors.initials: J
authors.lastname: Aguilar-Fuentes
authors.forename: Mario
authors.initials: M
authors.lastname: Zurita
authors.forename: Alfonso
authors.initials: A
authors.lastname: León-Del-Río
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D019731:Carbon-Nitrogen Ligases / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000201:enzymology; D002843:Chromatin / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics; D056945:Hep G2 Cells; D006657:Histones / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D008969:Molecular Sequence Data; D059007:Polytene Chromosomes / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D016415:Sequence Alignment
chemical_list: D000906:Antibodies; D002843:Chromatin; D050884:HSP72 Heat-Shock Proteins; D006657:Histones; D019731:Carbon-Nitrogen Ligases; C023312:holocarboxylase synthetases