Fig. 7: Model of intrinsic chromatin features regulating orientation-specific joining of CSR for generating productive antibodies in different species.
From: Chromatin-intrinsic mechanisms determine orientation-specific class switch recombination
a Chromatin features of the Igh constant region in different species (such as Ginglymostoma cirratum, Danio rerio, Xenopus laevis, Alligator sinensis, Gallus gallus, Mus musculus, and Homo sapiens) throughout evolution. The columns with different colors indicate different CH units. The green arrows indicate the transcription orientation. b long-distance CHs under the same transcriptional orientation within the Igh domain promote orientation-biased deletional joining of CSR for generating productive antibodies in some species, such as Mus musculus. Chromatin loop extrusion might promote this orientation-biased end joining for highly efficient CSR. c Opposite transcribed CHs, short-distance CHs, or different chromatin domain-isolated CHs promote inversional joining-mediated productive CSR in some species, such as Gallus gallus. Short-range diffusion might promote this relatively less-efficient CSR. The red bricks indicate the anchors for mediating TAD formation. The blue circles indicate the cohesin rings. The light red circle indicates the CSR center. The pink circle indicates the short-range diffusion area. The black arrows indicate the transcription orientation. The blue arrows indicate chromatin loop extrusion-mediated pulling force. The dotted arrows indicate the potential joining events between donor Sμ and acceptor Sx breaks. The key elements, such as donor Sμ (red oval), activated acceptor Sx (green oval), iEμ (atrovirens oval), and 3′RR (blue oval), are also indicated.
