MKRN1_C is the very C-terminus of E3 ubiquitin-protein ligase makorin-1, or MKRN1, a family of eukaryotic putative ribonucleoproteins with a distinctive array of zinc-finger motifs. MKRN1 plays an important role in modulating the homeostasis of telomere-length through a dynamic balance involving the stability of the protein hTERT. MKRN1 has been shown to be a a transcriptional co-regulator and an E3 ligase. It functions simultaneously as a differentially negative regulator of p53 and p21, preferentially leading cells to p53-dependent apoptosis by suppressing p21. The exact function of the C-terminal region has not been determined.