Characterization of the interactions between Codanin-1 and C15Orf41, two proteins implicated in Congenital dyserythropoietic anemia type I disease

Abstract

Background Congenital dyserythropoietic anemia type I (CDA I), is an autosomal recessive disease with macrocytic anemia in which erythroid precursors in the bone marrow exhibit pathognomonic abnormalities including spongy heterochromatin and chromatin bridges. We have shown previously that the gene mutated in CDA I encodes Codanin-1, a ubiquitously expressed and evolutionarily conserved large protein. Recently, an additional etiologic factor for CDA I was reported, C15Orf41, a predicted nuclease. Mutations in both CDAN1 and C15Orf41 genes results in very similar erythroid phenotype. However, the possible relationships between these two etiologic factors is not clear. the sequence of Codanin-1 protein does not resemble any known protein.Results We demonstrate here that Codanin-1 and C15Orf41 bind to each other, and that Codanin-1 stabilizes C15Orf41. C15Orf41 protein is mainly nuclear and Codanin-1 overexpression shifts it to the cytoplasm. Phylogenetic analyses demonstrated that even though Codanin-1 is an essential protein in mammals, it was lost from several diverse and unrelated animal taxa. Interestingly, C15Orf41 was eliminated in the exact same animal taxa. This is an extreme case of the Phylogenetic Profiling phenomenon, which strongly suggests common pathways for these two proteins. Lastly, as the 3D structure is more conserved through evolution than the protein sequence, we have used the Phyre2 alignment program to find structurally homologous proteins. We found that Codanin-1 is highly similar to CNOT1, a conserved protein which serves as a scaffold for proteins involved in mRNA stability and transcriptional control. Conclusions The physical interaction and the stabilization of C15Orf41 by Codanin-1, combined with the phylogenetic co-existence and co-loss of these two proteins during evolution, suggest that the major function of the presumptive scaffold protein, Codanin-1, is to regulate C15Orf41 activities. The similarity between Codanin-1 and CNOT1 suggest that Codanin-1 is involved in RNA metabolism and activity, and opens up a new avenue for the study of the molecular pathways affected in CDAI.

The congenital dyserythropoieitic anemias: genetics and pathophysiology

“…Consistent with these results, concurrent overexpression of Codanin-1 and CDIN1 results in higher CDIN1 level compared with overexpression of CDIN1 alone [30 ▪ ]. Interestingly, the cellular localization of CIDN1 appears to also depend on Codanin-1; combined overexpression of Codanin-1 and CDIN1 results in a shift in the localization of CDIN1 from the nucleus to the cytoplasm [30 ▪ ,36 ▪ ]. In contrast, two recent reports suggested that at the endogenous level of expression, CDIN1 localizes (with Codanin-1) primarily to the nucleolus by immunofluorescence [3 ▪ ,31 ▪ ]; while intriguing, this finding remains to be confirmed with an antibody validated for immunofluorescence [3 ▪ ,31 ▪ ].…”

“…Although reduced expression of CDIN1 had no impact on the Codanin-1 level, loss of Codanin-1 resulted in concurrent depletion of CDIN1 [3 ▪ ], suggesting that the stability of CDIN1 depends on Codanin-1. Consistent with these results, concurrent overexpression of Codanin-1 and CDIN1 results in higher CDIN1 level compared with overexpression of CDIN1 alone [30 ▪ ]. Interestingly, the cellular localization of CIDN1 appears to also depend on Codanin-1; combined overexpression of Codanin-1 and CDIN1 results in a shift in the localization of CDIN1 from the nucleus to the cytoplasm [30 ▪ ,36 ▪ ].…”

“…Initial efforts aimed at studying the function of Codanin-1 were performed using a cervical cancer cell line (HeLa) and an osteosarcoma cell line (U-2-OS); these studies demonstrated that Codanin-1 localizes to the heterochromatin during interphase and cytokinesis, but that Codanin-1 was phosphorylated during mitosis resulting in its exclusion from condensed chromosomes [28]. In contrast, three independent reports [27,29,30 ▪ ], two of which used validated antibodies [27,29], showed that Codanin-1 is localized mostly to the cytosol [27,29,30 ▪ ], a finding confirmed at the endogenous expression level in primary human erythroblasts, CDA I erythroblasts, and murine erythroblasts [27]. Although one of the latter reports showed that the Golgi apparatus of CDA I erythroblasts aberrantly accumulates HP1ɑ (a member of the heterochromatin protein family) [27], another report showed that Codanin-1 interacts with and sequesters Asf1 in the cytoplasm, resulting in inhibition of DNA replication because of impaired delivery of histones to the nucleus by Asf1 [29].…”

“…Since the discovery that ∼10% of CDA I patients have a mutation in CDIN1, several groups independently identified a physical interaction between the Codanin-1 and CDIN1 proteins [3 ▪ ,30 ▪ ,36 ▪ ]. Although reduced expression of CDIN1 had no impact on the Codanin-1 level, loss of Codanin-1 resulted in concurrent depletion of CDIN1 [3 ▪ ], suggesting that the stability of CDIN1 depends on Codanin-1.…”