CENPA

Centromere protein A, also known as CENPA, is a is_associated_with::protein which in humans is encoded by the CENPA is_associated_with::gene.

Function
is_associated_with::Centromeres are the chromosomal domains that specify the mitotic behavior of chromosomes. The CENPA gene encodes a centromere protein which contains a is_associated_with::histone H3 related histone fold domain that is required for targeting to the centromere. CENPA is proposed to be a component of a modified is_associated_with::nucleosome or nucleosome-like structure in which it replaces 1 or both copies of conventional histone H3 in the (H3-H4)2 tetrameric core of the nucleosome particle. is_associated_with::Alternative splicing results in multiple transcript variants encoding distinct is_associated_with::isoforms.

In higher eukaryotes, the recruitment of CENP-A nucleosomes to existing centromeres is an epigenetic process, independent of the underlying DNA sequence. In S.pombe, de novo recruitment of the CENP-A to the centromere is believed to be controlled by "centromeric" is_associated_with::heterochromatin surrounding the centromere, and by an is_associated_with::RNAi mechanism. The RNAi is cut to form is_associated_with::siRNA; this complexes with the protein Chp1, which then binds the centromeric heterochromatin. This helps recruit other proteins, ultimately resulting in a protein complex that forms is_associated_with::cohesin between two is_associated_with::sister chromatids at the centromeric heterochromatin. This cohesin is believed to be essential in replacing the centromere H3 with CENP-A. CENP-A is one of the is_associated_with::epigenetic changes that is believed to distinguish centromeric DNA from other DNA. Once the CENP-A has been added, the centromere becomes self-propagating, and the surrounding heterochromatin/RNAi mechanism is no longer necessary.