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Updated: Oct 30, 2025

CD Spectroscopy to Study DNA-Protein Interactions
Published on: February 10, 2022
R-loops mediate transcription-associated formation of human rDNA secondary constrictions
Hong Zhou1,2, Yapei Wang1,3, Qing Wang1
1Department of Genetics, College of Life Sciences, Wuhan University, Wuhan, China.
Abstract:
The ribosomal gene DNA (rDNA) often forms secondary constrictions in the chromosome; however, the molecular mechanism involved remains poorly understood. Here, we report that occurrence of rDNA constriction was increased in the chromosomes in human cancer cell lines compared with normal cells and that decondensed rDNA was significantly enhanced after partial inhibition of rDNA transcription. rDNA transcription was found during the S phase when replication occurred, and thus, DNA replication inhibitors caused constriction formation through hindering rDNA transcription. Inhibition of ataxia ATR (telangiectasia-mutated and RAD3-related) induced rDNA constriction formation. Replication stress or transcription inhibition increased R-loop formation. Topoisomerase I and RNase H1 suppressed secondary constriction formation. These data demonstrate that transcription stress causes the accumulation of stable R-loops (RNA-DNA hybrid) and subsequent constriction formation in the chromosomes.
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