1. Xist RNA
Xist RNA is noncoding RNA coats the inactive X-chromosome in regions of heterochromatin.
Xist RNA was subsequently found to physically coat the inactive-X chromosome, and studies in mice demonstrated that Xist remains associated with the inactive-X during mitosis.
The presence of Xist on the mitotic inactive-X supports its role as the transmitter of the epigenetic state of the inactive-X from one cell division cycle to the next. In human cells, however, Xist RNA appears to dissociate from the X-chromosome during mitosis.