Neocentromeres not contain endogenous DNA centromeres characteristic , i.e. systems tandem repeat sequence ; Thus, the type of DNA that makes the neocentromerów . Create neocentromerów done by epigenetic mechanisms . It is likely that the center of creating neocentromerów serialized euchromatynowych chromosomes could be mobile elements that frequently occur in eukaryotic genomes and are also present in the right centromere and adjacent to the heterochromatin przycentromerowej . The test results by immunoprecipitation showed that the key protein CENP-A/CENH3 that determine the formation of the centromere , associated with retorelementami . Overexpression of this protein in Drosophila causes its appearance in niecentromerowych chromosomes and formation of functional neocentromerów polycentric chromosomes , resulting in numerous interference in mitosis . And a mechanism to prevent excess CID ( CENP -A homolog of Drosophila ) involves proteolytic cleavage of the protein unrelated to the centromeres . The use of fusion proteins CENP -A and its homologs - GFP / YFP / EYEP allowed the conclusion that most higher eukaryotes synthesis and assembly of this protein into the centromeric chromatin nucleosomes is held in the G2 phase , in Drosophila - S -phase , while in yeast - during S and G2. The centromere -specific mounting CENP-A/CENH3 decides presence in their C -terminal end of the target domain , catd . Mounting CENP -A and homologues also occurs in the absence of species- specific N- teminalnego end . An integral part of the region centromeric heterochromatin is , the current in the right centromere and the region przycentromerowym . The endogenous centromeres in heterochromatin exhibits all the epigenetic characteristics specific to the heterochromatin and transcriptionally inactive condensed chromatin : DNA methylation , methylations lysines 9 and 27 on histone H3 lysine 20 and histone H4 in , no acetylation of H3 and H4 , the presence of HP1 proteins . These modifications occur in the region around neocentromerowym euchromatyny created , but to a lesser extent than in the endogenous centromeres . Cohesin , resulting in adhesion of sister chromatids appears with playback chromatin , after DNA replication , and preferentially binds to heterochromatynowymi regions , which come last when heterochromatin przycentromerowej disappears . Cohesin binding has recently been shown to sections euchromatynowych . When changes occur in the evolution of the chromosomal location due to their centromeres and the formation neocentromerów deactivation . Experimental data obtained so far on creating neocentromerów are few still do not know why neocentromeres formed in both regions eu - and heterochromatin and at - outside the inactivation of endogenous centromere - causes their appearance .