Plant centromeres are generally composed of tandem arrays of simple repeats that form a complex chromosome locus where the kinetochore forms and microtubules attach during mitosis and meiosis. Each chromosome has one ...Plant centromeres are generally composed of tandem arrays of simple repeats that form a complex chromosome locus where the kinetochore forms and microtubules attach during mitosis and meiosis. Each chromosome has one centromere region, which is essential for accurate division of the genetic material. Recently, chromosomes containing two centromere regions （called dicentric chromosomes） have been found in maize and wheat. Interestingly, some dicentric chromosomes are stable because only one centromere is active and the other one is inactivated. Because such arrays maintain their typical structure for both active and inactive centromeres, the specification of centromere activity has an epigenetic component independent of the DNA sequence. Under some circumstances, the inactive centromeres may recover centromere function, which is called centromere reactivation. Recent studies have highlighted the important changes, such as DNA methylation and histone modification, that occur during centromere inactivation and reactivation.展开更多
A set of proteins and noncoding RNAs, referred to as the male specific lethal （MSL） complex, is present on the male X chromosome in Drosophila and has been postulated to be responsible for dosage compensation of thi...A set of proteins and noncoding RNAs, referred to as the male specific lethal （MSL） complex, is present on the male X chromosome in Drosophila and has been postulated to be responsible for dosage compensation of this chromosome -- the up-regulation of its expression to be equal to that of two X chromosomes in females. This hypothesis is evaluated in view of lesser known aspects of dosage compensation such as the fact that metafemales with three X chromosomes also have equal expression to normal females, which would require a down-regulation of each gene copy Moreover, when this complex is ectopically expressed in females or specifically targeted to a reporter in males, there is no increase in expression of the genes or targets with which it is associated. These observations are not consistent with the hypothesis that the MSL complex conditions dosage compensation. A synthesis is described that can account for these observations.展开更多
基金supported by the grants from the National Natural Science Foundation of China (Nos.31071083 and 31130033)the National Science Foundation of USA (No.DBI 0922703)
文摘Plant centromeres are generally composed of tandem arrays of simple repeats that form a complex chromosome locus where the kinetochore forms and microtubules attach during mitosis and meiosis. Each chromosome has one centromere region, which is essential for accurate division of the genetic material. Recently, chromosomes containing two centromere regions （called dicentric chromosomes） have been found in maize and wheat. Interestingly, some dicentric chromosomes are stable because only one centromere is active and the other one is inactivated. Because such arrays maintain their typical structure for both active and inactive centromeres, the specification of centromere activity has an epigenetic component independent of the DNA sequence. Under some circumstances, the inactive centromeres may recover centromere function, which is called centromere reactivation. Recent studies have highlighted the important changes, such as DNA methylation and histone modification, that occur during centromere inactivation and reactivation.
基金supported by the National Institutes of Health grant of the United States(No.RO1GM068042)
文摘A set of proteins and noncoding RNAs, referred to as the male specific lethal （MSL） complex, is present on the male X chromosome in Drosophila and has been postulated to be responsible for dosage compensation of this chromosome -- the up-regulation of its expression to be equal to that of two X chromosomes in females. This hypothesis is evaluated in view of lesser known aspects of dosage compensation such as the fact that metafemales with three X chromosomes also have equal expression to normal females, which would require a down-regulation of each gene copy Moreover, when this complex is ectopically expressed in females or specifically targeted to a reporter in males, there is no increase in expression of the genes or targets with which it is associated. These observations are not consistent with the hypothesis that the MSL complex conditions dosage compensation. A synthesis is described that can account for these observations.
