Nuclear nucleic acid-binding protein C1D, also known as C1D, plays a role in the recruitment of the RNA exosome complex to pre-rRNA to mediate the 3'-5' end processing of the 5.8S rRNA; this function may include MPHOSPH6. This protein can activate PRKDC not only in the presence of linear DNA but also in the presence of supercoiled DNA. This protein can induce apoptosis in a p53/TP53 dependent manner. Recombinant human C1D protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.