title: Interplay between chromatin and trans-acting factors regulating the Hoxd4 promoter during neural differentiation.
abstract: Correct patterning of the antero-posterior axis of the embryonic trunk is dependent on spatiotemporally restricted Hox gene expression. In this study, we identified components of the Hoxd4 P1 promoter directing expression in neurally differentiating retinoic acid-treated P19 cells. We mapped three nucleosomes that are subsequently remodeled into an open chromatin state upon retinoic acid-induced Hoxd4 transcription. These nucleosomes spanned the Hoxd4 transcriptional start site in addition to a GC-rich positive regulatory element located 3' to the initiation site. We further identified two major cis-acting regulatory elements. An autoregulatory element was shown to recruit HOXD4 and its cofactor PBX1 and to positively regulate Hoxd4 expression in differentiating P19 cells. Conversely, the Polycomb group (PcG) protein Ying-Yang 1 (YY1) binds to an internucleosomal linker and represses Hoxd4 transcription before and during transcriptional activation. Sequential chromatin immunoprecipitation studies revealed that the PcG protein MEL18 was co-recruited with YY1 only in undifferentiated P19 cells, suggesting a role for MEL18 in silencing Hoxd4 transcription in undifferentiated P19 cells. This study links for the first time local chromatin remodeling events that take place during transcriptional activation with the dynamics of transcription factor association and DNA accessibility at a Hox regulatory region.
authors.affiliation: McGill Cancer Centre, McGill University, Montréal, Québec H3G 1Y6 Canada.
authors.forename: Laila
authors.initials: L
authors.lastname: Kobrossy
authors.forename: Mojgan
authors.initials: M
authors.lastname: Rastegar
authors.forename: Mark
authors.initials: M
authors.lastname: Featherstone
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009707:Nucleosomes / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014212:Tretinoin / Q000378:metabolism; D050986:YY1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D002843:Chromatin; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C489520:Hoxd4 protein, mouse; D009707:Nucleosomes; C066476:Pcgf6 protein, mouse; D034741:RNA, Small Interfering; D014157:Transcription Factors; D050986:YY1 Transcription Factor; D014212:Tretinoin; D063150:Polycomb Repressive Complex 1