Heterochromatin Integrity Affects Chromosome Reorganization After Centromere Dysfunction

Abstract

The centromere is essential for the inheritance of genetic information on eukaryotic chromosomes. Epigenetic regulation of centromere identity has been implicated in genome stability, karyotype evolution, and speciation. However, little is known regarding the manner in which centromere dysfunction affects the chromosomal architectures. Here we show that in the fission yeast Schizosaccharomyces pombe, the conditional deletion of the centromere produces survivors that carry either a neocentromere-acquired chromosome at the subtelomeric region or an acentric chromosome rescued by intertelomere fusion with either of the remaining chromosomes. The ratio of neocentromere formation to telomere fusion is considerably decreased by the inactivation of genes involved in RNA interference-dependent heterochromatin formation. By affecting the modes of chromosomal reorganization, the genomic distribution of heterochromatin may influence the fate of karyotype evolution.

Maize centromeres expand and adopt a uniform size in the genetic background of oat

“…Insertion of a marker gene in the centromeres of Schizosaccharomyces pombe chromosomes results in complete silencing of the gene (Allshire et al 1995). Similarly, neocentromeres in multiple species generally form in gene-poor regions (Lomiento et al 2008;Alonso et al 2010;Shang et al 2013); when they do form over genic areas, the affected genes are suppressed or silenced (Ishii et al 2008;Ketel et al 2009;Shang et al 2013). Why does centromeric chromatin avoid actively transcribed genes?…”

“…One way to study centromere repositioning is to focus on newly established centromeres known as neocentromeres. There are many known neocentromere examples in human clinical samples (Voullaire et al 1993;Marshall et al 2008) as well as in different animal and plant species (Williams et al 1998;Maggert and Karpen 2001;Nasuda et al 2005;Ishii et al 2008;Ketel et al 2009;Topp et al 2009;Fu et al 2013). Most newly formed neocentromeres lie in moderately repetitive genomic regions interspersed with single-copy sequences (Marshall et al 2008), whereas nearly all mature centromeres contain long arrays of satellite repeats (Henikoff et al 2001;Jiang et al 2003).…”

Euchromatic Subdomains in Rice Centromeres Are Associated with Genes and Transcription

“…Neocentromere formation in S. pombe can negatively impact the transcription of the underlying endogenous genes (Ishii et al, 2008). Similarly, neocentromere formation can cause silencing of the underlying transgene in C. albicans (Ketel et al, 2009).…”

The Centromere: Epigenetic Control of Chromosome Segregation during Mitosis

“…Importantly, CENP-A is present at the site of all functional neocentromeres, but is lost from the original centromeric locus concurrent with endogenous centromere silencing (Warburton et al 1997;Lo et al 2001). In Schizosaccharomyces pombe, deletion of a centromere is rescued by spontaneous neocentromere formation typically close to telomeric regions, and is dependent on formation of heterochromatin (Ishii et al 2008;Kagansky et al 2009). …”

“…In particular, H3K4me2 appears to be a centromere-specific modification that has been shown to promote CENP-A assembly into chromatin (Bergmann et al 2011). In S. pombe, artificial tethering of the histone methyltransferase Clr4 to euchromatin promotes neocentromere formation (Ishii et al 2008). Targeting of transcriptional activators and repressors to human artificial chromosome (HAC) centromeres influences kinetochore formation and CENP-A assembly, although the precise mechanisms remain largely unclear (Nakano et al 2008;Cardinale et al 2009;Ohzeki et al 2012).…”