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The MukB-topoisomerase IV interaction is required for proper chromosome compaction.

ABSTRACT: The bacterial condensin MukB and the cellular decatenating enzyme topoisomerase IV interact. This interaction stimulates intramolecular reactions catalyzed by topoisomerase IV, supercoiled DNA relaxation, and DNA knotting but not intermolecular reactions such as decatenation of linked DNAs. We have demonstrated previously that MukB condenses DNA by sequestering negative supercoils and stabilizing topologically isolated loops in the DNA. We show here that the MukB-topoisomerase IV interaction stabilizes MukB on DNA, increasing the extent of DNA condensation without increasing the amount of MukB bound to the DNA. This effect does not require the catalytic activity of topoisomerase IV. Cells carrying a mukB mutant allele that encodes a protein that does not interact with topoisomerase IV exhibit severe nucleoid decompaction leading to chromosome segregation defects. These findings suggest that the MukB-topoisomerase IV complex may provide a scaffold for DNA condensation.

SUBMITTER: Kumar R

PROVIDER: S-EPMC5641886 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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The MukB-topoisomerase IV interaction is required for proper chromosome compaction.

Kumar Rupesh R Nurse Pearl P Bahng Soon S Lee Chong M CM Marians Kenneth J KJ

The Journal of biological chemistry 20170825 41

The bacterial condensin MukB and the cellular decatenating enzyme topoisomerase IV interact. This interaction stimulates intramolecular reactions catalyzed by topoisomerase IV, supercoiled DNA relaxation, and DNA knotting but not intermolecular reactions such as decatenation of linked DNAs. We have demonstrated previously that MukB condenses DNA by sequestering negative supercoils and stabilizing topologically isolated loops in the DNA. We show here that the MukB-topoisomerase IV interaction sta ...[more]

PMID: 28842485

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Project description:Dosage compensation refers to the equalization of most X-linked gene products between males and females. In Drosophila, it is mediated by the MSL complex that preferentially associates with numerous sites on the X chromosome in somatic cells of males, and is responsible for an enhancement of the transcriptional rate of a substantial number of X-linked genes. Here we show that topoisomerase II (Topo II) is an integral part of the mechanistic basis of dosage compensation and we highlight a novel function for this enzyme. A widely accepted model of transcription postulates that the moving bubble generated by an RNA polymerase elongating complex induces positive DNA supercoiling in the region ahead of the complex and negative supercoiling in its wake. These transitory changes in supercoiling are resolved by the action of topoisomerases. We have investigated the role of Topo II in dosage compensation by RNAi-mediated depletion, and we have used chromatin immunoprecipitation to determine its genomic distribution and relative abundance on X-linked genes. Topo II is enriched on dosage compensated genes and this enrichment is independent from the approximate two-fold enhancement in transcription of these genes. We have demonstrated an RNA-dependent association of Topo II with MLE, the ATPase-helicase subunit of the MSL complex. Our results indicate a role for Topo II that is additional to and different from its function in restoring normal DNA superhelicity during the transcription process. We suggest that the enhanced level of Topo II alters the DNA supercoiling of compensated gene units to facilitate transcription and could provide a basis for the recent report that the MSL complex enhances transcription by increasing the rate of elongation of RNA polymerase II. Investigation of dosage compensated gene expression levels in S2 and S2 Topo II RNAi knockdown cells. mRNA was isolated from S2 cells and S2 cells with RNAi knockdown of Topo II. The mRNA was then converted to cDNA and hybridized to a NimbleGen D. melanogaster gene expression array. 2 replicates each.

Dataset Information

The MukB-topoisomerase IV interaction is required for proper chromosome compaction.

Publications

The MukB-topoisomerase IV interaction is required for proper chromosome compaction.

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