This is the C-terminal K-rich domain from RNA polymerase I-specific transcription initiation factor Rrn6 [1]. Rrn6 is a component of a multisubunit transcription factor essential for the initiation of rDNA transcription by Pol I [1,2].

1: Structural Basis of RNA Polymerase I Transcription Initiation. Engel C, Gubbey T, Neyer S, Sainsbury S, Oberthuer C, Baejen C, Bernecky C, Cramer P; Cell. 2017;169:120-131. PMID:28340337

2: RRN6 and RRN7 encode subunits of a multiprotein complex essential for the initiation of rDNA transcription by RNA polymerase I in Saccharomyces cerevisiae. Keys DA, Vu L, Steffan JS, Dodd JA, Yamamoto RT, Nogi Y, Nomura M; Genes Dev. 1994;8:2349-2362. PMID:7958901