Biomaterial Database

Recent advances in X-chromosome inactivation. 2004

Edith Heard

CNRS UMR 218, Curie Institute, 26 rue d'Ulm, Paris 75005, France. Edith.Heard@curie.fr

X inactivation is the silencing one of the two X chromosomes in XX female mammals. Initiation of this process during early development is controlled by the X-inactivation centre, a complex locus that determines how many, and which, X chromosomes will be inactivated. It also produces the Xist transcript, a remarkable RNA that coats the X chromosome in cis and triggers its silencing. Xist RNA coating induces a cascade of chromatin changes on the X chromosome, including the recruitment of Polycomb group proteins. This results in an inactive state that is initially labile, but may be further locked in by epigenetic marks such as DNA methylation. In mice, X inactivation has recently been found to be much more dynamic than previously thought during early pre-implantation development. The paternal X chromosome is initially inactivated in all cells of cleavage-stage embryos and then selectively reactivated in the subset of cells that will form the embryo, with random X inactivation occurring thereafter.

UI	MeSH Term	Description	Entries
D012097	Repressor Proteins	Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.	Repressor Molecules,Transcriptional Silencing Factors,Proteins, Repressor,Silencing Factors, Transcriptional
D002843	Chromatin	The material of CHROMOSOMES. It is a complex of DNA; HISTONES; and nonhistone proteins (CHROMOSOMAL PROTEINS, NON-HISTONE) found within the nucleus of a cell.	Chromatins
D004303	Dosage Compensation, Genetic	Genetic mechanisms that allow GENES to be expressed at a similar level irrespective of their GENE DOSAGE. This term is usually used in discussing genes that lie on the SEX CHROMOSOMES. Because the sex chromosomes are only partially homologous, there is a different copy number, i.e., dosage, of these genes in males vs. females. In DROSOPHILA, dosage compensation is accomplished by hypertranscription of genes located on the X CHROMOSOME. In mammals, dosage compensation of X chromosome genes is accomplished by random X CHROMOSOME INACTIVATION of one of the two X chromosomes in the female.	Dosage Compensation (Genetics),Gene Dosage Compensation,Hypertranscription, X-Chromosome,X-Chromosome Hypertranscription,Compensation, Dosage (Genetics),Compensation, Gene Dosage,Compensation, Genetic Dosage,Dosage Compensation, Gene,Gene Dosage Compensations,Genetic Dosage Compensation,Genetic Dosage Compensations,Hypertranscription, X Chromosome,X Chromosome Hypertranscription
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014960	X Chromosome	The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species.	Chromosome, X,Chromosomes, X,X Chromosomes
D062085	RNA, Long Noncoding	A class of untranslated RNA molecules that are typically greater than 200 nucleotides in length and do not code for proteins. Members of this class have been found to play roles in transcriptional regulation, post-transcriptional processing, CHROMATIN REMODELING, and in the epigenetic control of chromatin.	LincRNA,RNA, Long Untranslated,LINC RNA,LincRNAs,Long Intergenic Non-Protein Coding RNA,Long Non-Coding RNA,Long Non-Protein-Coding RNA,Long Noncoding RNA,Long ncRNA,Long ncRNAs,RNA, Long Non-Translated,lncRNA,Long Intergenic Non Protein Coding RNA,Long Non Coding RNA,Long Non Protein Coding RNA,Long Non-Translated RNA,Long Untranslated RNA,Non-Coding RNA, Long,Non-Protein-Coding RNA, Long,Non-Translated RNA, Long,Noncoding RNA, Long,RNA, Long Non Translated,RNA, Long Non-Coding,RNA, Long Non-Protein-Coding,Untranslated RNA, Long,ncRNA, Long,ncRNAs, Long
D019175	DNA Methylation	Addition of methyl groups to DNA. DNA methyltransferases (DNA methylases) perform this reaction using S-ADENOSYLMETHIONINE as the methyl group donor.	DNA Methylations,Methylation, DNA,Methylations, DNA
D022661	RNA, Untranslated	RNA which does not code for protein but has some enzymatic, structural or regulatory function. Although ribosomal RNA (RNA, RIBOSOMAL) and transfer RNA (RNA, TRANSFER) are also untranslated RNAs they are not included in this scope.	Noncoding RNA,RNA, Non-Coding,RNA, Non-Peptide-Coding,RNA, Non-Protein-Coding,RNA, Noncoding,RNA, Nontranslated,npcRNA,Non-Coding RNA,Non-Peptide-Coding RNA,Non-Protein-Coding RNA,Nontranslated RNA,RNA, Non Coding,RNA, Non Peptide Coding,RNA, Non Protein Coding,Untranslated RNA
D063146	Polycomb-Group Proteins	A family of proteins that play a role in CHROMATIN REMODELING. They are best known for silencing HOX GENES and the regulation of EPIGENETIC PROCESSES.	PcG Complex Protein,Polycomb Group Protein,Polycomb Repressive Complex Protein,Polycomb-Group Protein,Polycomb-Group Protein Complex,PRC1-Like Complex,PcG Complex Proteins,Polycomb Group (PcG) Multiprotein PRC1-Like Complex,Polycomb Repressive Complex Proteins,Polycomb-Group Protein Complexes,Complex Protein, PcG,Complex, PRC1-Like,Complex, Polycomb-Group Protein,Complexes, Polycomb-Group Protein,Group Protein, Polycomb,PRC1 Like Complex,Polycomb Group Protein Complex,Polycomb Group Protein Complexes,Polycomb Group Proteins,Protein Complex, Polycomb-Group,Protein Complexes, Polycomb-Group,Protein, PcG Complex,Protein, Polycomb Group,Protein, Polycomb-Group