has been proposed that these transcription factors cause splicing to occur at intron 1 at the binding site of these factors on the Xist gene, which inhibits Xist expression A study was conducted where Nanog or Oct4 transcription factors were depleted in pluripotent cells, which resulted in the upregulation of Xist. From this study, it is proposed that Nanog and Oct4 are involved in the repression of Xist expression. Polycomb repressive complex Polycomb repressive complex 2 (PRC2) consist of a class of polycomb group proteins that are involved in catalyzing the trimethylation of histone H3 on lysine 27 (K27), which results in chromatin repression, and thus leads to transcriptional silencing. Xist RNA recruits polycomb complexes to the inactive X chromosome at the onset of XCI. SUZ12 is a component of the PRC2 and contains a zinc finger domain. The zinc finger domain is believed to bind to the RNA molecule. The PRC2 has been observed to repress Xist expression independent of the Tsix antisense transcript, although the definite mechanism is still not known. Dosage compensation X-inactivation plays a key role in dosage compensation mechanisms that allow for equal expression of the X and autosomal chromosomes. Different species have different dosage compensation methods, with all of the methods involving the regulation of an X chromosome from one of the either sexes. Some methods involved in dosage compensation to inactivate one of the X chromosomes from one of the sexes are Tsix antisense gene, DNA methylation and DNA acetylation; however, the definite mechanism of X-inactivation is still poorly understood. If one of the X chromosomes is not inactivated or is partially expressed, it could lead to over expression of the X chromosome and it could be lethal in some cases. Turner's Syndrome is one example of where dosage compensation does not equally express the X chromosome, and in females one of the X chromosomes is missing or has abnormalities, which leads to physical abnormalities and also gonadal dysfunction in females due to the one missing or abnormal X chromosome. Turner's syndrome is also referred to as a monosomy X condition. X-inactivation cycle Xist expression and X-inactivation change throughout embryonic development. In early embryogenesis, the oocyte and sperm do not express Xist and the X chromosome remains active. After fertilization, when the cells are in the 2 to 4 cell stage, Xist transcripts are expressed from parent X chromosome(Xp) in every cell, causing