dosage compensation by inactivation of X chromosome
Definition
Target type: biologicalprocess
Compensating for the two-fold variation in X-chromosome:autosome ratios between sexes by heterochromatin formation leading to a global inactivation of all, or most of, the genes on one of the X-chromosomes in the XX sex. [GOC:jl, GOC:mr, GOC:pr, PMID:11498577, PMID:20622855, Wikipedia:XY_sex-determination_system]
Dosage compensation is a biological process that equalizes the expression of X-linked genes between males and females, despite the difference in the number of X chromosomes. In mammals, females have two X chromosomes while males have one X and one Y chromosome. To ensure that females do not produce twice the amount of X-linked gene products compared to males, one of the two X chromosomes in females undergoes inactivation during early embryonic development. This process, known as X chromosome inactivation (XCI), involves the silencing of most genes on one X chromosome in each cell of a female. XCI is a complex process that is initiated by a non-coding RNA called Xist. Xist RNA coats the X chromosome that will be inactivated and recruits protein complexes that modify the chromatin structure, leading to gene silencing. The inactive X chromosome becomes highly condensed and appears as a Barr body in the nucleus. The choice of which X chromosome is inactivated is random in each cell during early development, and once a decision is made, it is maintained in all subsequent daughter cells. This random inactivation leads to a mosaic pattern of X chromosome expression in females, where some cells express the maternal X chromosome and others express the paternal X chromosome. XCI is essential for proper development in females and plays a critical role in the regulation of X-linked gene expression. It serves to balance gene dosage between the sexes and prevents potentially detrimental imbalances in the expression of X-linked genes.'
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Proteins (1)
| Protein | Definition | Taxonomy |
|---|---|---|
| N6-adenosine-methyltransferase catalytic subunit | An N6-adenosine-methyltransferase catalytic subunit that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q86U44] | Homo sapiens (human) |
Compounds (1)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| s-adenosylhomocysteine | S-adenosyl-L-homocysteine : An organic sulfide that is the S-adenosyl derivative of L-homocysteine. S-Adenosylhomocysteine: 5'-S-(3-Amino-3-carboxypropyl)-5'-thioadenosine. Formed from S-adenosylmethionine after transmethylation reactions. | adenosines; amino acid zwitterion; homocysteine derivative; homocysteines; organic sulfide | cofactor; EC 2.1.1.72 [site-specific DNA-methyltransferase (adenine-specific)] inhibitor; EC 2.1.1.79 (cyclopropane-fatty-acyl-phospholipid synthase) inhibitor; epitope; fundamental metabolite |