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Transcription Loops Video

The cartoon shows how transcription initiation and termination of a highly expressed gene lead to formation and disappearance of a transcription loop. The sequence of the events:

  • a gene body (orange thread) is coiled within a locus (blue threads) in a compact structure;
  • upon transcription initiation, RNAPIIs (dark grey oval structures) are loading at the gene promoter (red) and begin to elongate;
  • during elongation, nRNPs appear and grow in size (depicted as grey amorphous structures);
  • during a transcription pause, chromatin of the gene is coiled and forms a sliding knot (orange thread), dynamically formed beyond the last RNAPII of the first burst and disentangled by first RNAPII of the second burst;
  • dense decoration with voluminous nRNP rigidifies the gene axis and forces its expansion, as well as the divergence of gene flanks (blue threads);
  • RNAPIIs of the first transcription burst reach the 3’ gene end, release attached nRNPs and dissociate from the gene;
  • the sliding chromatin knot reaches the 3’ gene end;
  • RNAPIIs stop loading at the promoter at the end of the second burst;
  • gene condensation starts 5’-terminally;
  • the gene flanks begin to converge;
  • the gene returns to its coiled compact state.

Animation: Irina Solovei, Jack Bates, Susanne Leidescher and artists Dimitar Kralev & Tamako Suzuki