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 [1]. MKRN1 plays an important role in modulating the homeostasis of telomere-length through a dynamic balance involving the stability of the protein hTERT [2]. 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 [3]. The exact function of the C-terminal region has not been determined.

1: The ancient source of a distinct gene family encoding proteins featuring RING and C(3)H zinc-finger motifs with abundant expression in developing brain and nervous system. Gray TA, Hernandez L, Carey AH, Schaldach MA, Smithwick MJ, Rus K, Marshall Graves JA, Stewart CL, Nicholls RD; Genomics. 2000;66:76-86. PMID:10843807

2: Ubiquitin ligase MKRN1 modulates telomere length homeostasis through a proteolysis of hTERT. Kim JH, Park SM, Kang MR, Oh SY, Lee TH, Muller MT, Chung IK; Genes Dev. 2005;19:776-781. PMID:15805468

3: Differential regulation of p53 and p21 by MKRN1 E3 ligase controls cell cycle arrest and apoptosis. Lee EW, Lee MS, Camus S, Ghim J, Yang MR, Oh W, Ha NC, Lane DP, Song J; EMBO J. 2009;28:2100-2113. PMID:19536131