Association of a centromere specific nucleosome with the yeast plasmid partitioning locus

Jayaram, Makkuni

doi:10.4161/mge.1.3.17431

Cited by 1 publication

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“…A variety of host factors that associate with centromeres and play important functional roles in faithful chromosome segregation are also detected at the STB locus, and nearly all of these appear to promote plasmid partitioning as well ( 32 , 35 – 38 ). The apparent functional resemblance between CEN and STB with respect to host factor association may suggest that the atypical, genetically defined point centromere of budding yeast and STB might have descended from a common ancestral partitioning locus ( 39 – 42 ). However, current evidence argues against the recruitment of kinetochore components at STB or the execution of plasmid segregation by directly utilizing spindle force ( 43 , 44 ).…”

Section: Introductionmentioning

confidence: 99%

Replication-dependent and independent mechanisms for the chromosome-coupled persistence of a selfish genome

Liu

Chang

et al. 2016

Nucleic Acids Res

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The yeast 2-micron plasmid epitomizes the evolutionary optimization of selfish extra-chromosomal genomes for stable persistence without jeopardizing their hosts’ fitness. Analyses of fluorescence-tagged single-copy reporter plasmids and/or the plasmid partitioning proteins in native and non-native hosts reveal chromosome-hitchhiking as the likely means for plasmid segregation. The contribution of the partitioning system to equal segregation is bipartite- replication-independent and replication-dependent. The former nearly eliminates ‘mother bias’ (preferential plasmid retention in the mother cell) according to binomial distribution, thus limiting equal segregation of a plasmid pair to 50%. The latter enhances equal segregation of plasmid sisters beyond this level, elevating the plasmid close to chromosome status. Host factors involved in plasmid partitioning can be functionally separated by their participation in the replication-independent and/or replication-dependent steps. In the hitchhiking model, random tethering of a pair of plasmids to chromosomes signifies the replication-independent component of segregation; the symmetric tethering of plasmid sisters to sister chromatids embodies the replication-dependent component. The 2-micron circle broadly resembles the episomes of certain mammalian viruses in its chromosome-associated propagation. This unifying feature among otherwise widely differing selfish genomes suggests their evolutionary convergence to the common logic of exploiting, albeit via distinct molecular mechanisms, host chromosome segregation machineries for self-preservation.

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