C-terminal zinc ribbon domain of RPA12 subunit of RNA polymerase I
The C-terminal zinc ribbon domain (C-ribbon) of subunit A12 (Zn-ribbon_RPA12) in RNA polymerase (Pol) I is involved in intrinsic transcript cleavage. Eukaryote genomes are transcribed by three nuclear RNA polymerases (Pol I, II and III) that share some subunits. RPA12 in Pol I, RPB9 in Pol II, RPC11 in Pol III and TFS in archaea are distantly related to each other and to the TFIIS elongation factor of Pol II. RPA12 has two zinc-binding domains separated by a flexible linker.
Comment:The zinc ribbon is the most conserved part of RPB9, RPC11, RPA12 subunits of RNA polymerases and it is homologous to TFIIS domain III and the C-terminal zinc ribbon domain of archaeal Transcription Factor S. Three antiparallel b-sheets are stabilized by a tetrad of cysteines that chelate zinc
Jiyao W et al.(2023). "The conserved domain database in 2023.",