Extended Data Fig. 4: The RPA34 extension tethers the heterodimer to the Pol I core.

a, Cartoon domain representation of the domain composition of the human RPA34 (top) and its yeast homologue A34.5 (bottom). The colored bar indicates the region modeled in the structure denoted as ‘built’. DM – dimerization domain. b, Multiple sequence alignment of the modeled portion of the RPA34 extension between different species listed on the left. Dark blue marks identical residues and light blue similar residues. Dots mark gaps in the sequence. c, RPA34 extension path (stick representation) on the Pol I surface (surface representation). Cryo-EM density, corresponding to the extension is shown in gray, transparent representation. Lower panels show the close up view of the extension (stick representation) surrounded by the Pol I core (cartoon representation). Residues from the Pol I core within the 5 Å radius from the linker are shown as sticks. Putative hydrogen bonds are shown as black dotted lines. d, Superposition of the yeast A34.5 extension from PDB: 4C3I2¹⁹ (navy) onto the human structure shown in the panel above.