Topological similarity between the 2μm plasmid partitioning locus and the budding yeast centromere: evidence for a common evolutionary origin?

Abstract

The partitioning locus STB of the selfish plasmid, the 2μm circle, of Saccharomyces cerevisiae is essential for the propagation of this multi-copy extra-chromosomal DNA element with nearly chromosome-like stability. The functional competence of STB requires the plasmid-coded partitioning proteins Rep1 and Rep2 as well as host-coded proteins. Host factors that associate with STB in a Rep1- and Rep2-dependent manner also interact with centromeres, and play important roles in chromosome segregation. They include the cohesin complex and the centromere-specific histone H3 variant Cse4. The genetically defined point centromere of S. cerevisiae differs starkly from the much more widespread epigenetically specified regional centromeres of eukaryotes. The particularly small size of the S. cerevisiae centromere and the association of chromosome segregation factors with STB raise the possibility of an evolutionary link between these two partitioning loci. The unusual positive supercoiling harboured by the S. cerevisiae centromere and STB in vivo in their functional states, unveiled by recent experiments, bolsters the notion of their potential descent from an ancestral plasmid partitioning locus.

A selfish DNA element engages a meiosis-specific motor and telomeres for germ-line propagation

“…A selfish DNA element engages a meiosis-specific motor and telomeres for germ-line propagation association of cohesin and Cse4 with STB (Ghosh et al, 2010;Huang et al, 2011b) raises concerns regarding their functional relevance, unless they act in a catalytic manner. Circumstantial evidence suggests that the atypical point CEN of budding yeasts and the STB locus might share an ancestor that once directed both chromosome and plasmid segregation (Malik and Henikoff, 2009;Huang et al, 2011a;Jayaram et al, 2013). The present day associations of CEN binding factors at STB may be relics of that shared evolutionary history.…”

The Rabl configuration limits topological entanglement of chromosomes in budding yeast

“…the cell nucleus) and simultaneously minimized with respect to the energy of the wormlike chain. To generate Rabl configurations the same annealing algorithm was used with the additional conditions that centromeres were clustered and telomeres were tethered to variable locations near their experimentally measured locations 79,80 . The energy potential that binds telomeres and centromeres to a specific location uses the L 1 norm, which allows for more movement at higher temperatures yet more restricted movement at lower temperatures, and a smoother transition during the cooling schedule (See SI for more details).…”

Topological Aspects of DNA Function and Protein Folding

“…Jorge Schvartzman et al [6] review the interplay between DNA supercoiling and DNA knotting during ongoing replication of bacterial chromosomes. Makkuni Jayaram et al [9] review the similarity between partitioning loci in yeast plasmids and chromosomes while discussing the unusual positive supercoiling that can be detected in the centromeric region. Makkuni Jayaram et al [9] review the similarity between partitioning loci in yeast plasmids and chromosomes while discussing the unusual positive supercoiling that can be detected in the centromeric region.…”