Identification and characterization of CHCHD1, AURKAIP1, and CRIF1 as new members of the mammalian mitochondrial ribosome

Abstract

Defects in mitochondrial ribosomal proteins (MRPs) cause various diseases in humans. Because of the essential role of MRPs in synthesizing the essential subunits of oxidative phosphorylation (OXPHOS) complexes, identifying all of the protein components involved in the mitochondrial translational machinery is critical. Initially, we identified 79 MRPs; however, identifying MRPs with no clear homologs in bacteria and yeast mitochondria was challenging, due to limited availability of expressed sequence tags (ESTs) in the databases available at that time. With the improvement in genome sequencing and increased sensitivity of mass spectrometry (MS)-based technologies, we have established four previously known proteins as MRPs and have confirmed the identification of ICT1 (MRP58) as a ribosomal protein. The newly identified MRPs are MRPS37 (Coiled-coil-helix-coiled-coil-helix domain containing protein 1-CHCHD1), MRPS38 (Aurora kinase A interacting protein1, AURKAIP1), MRPS39 (Pentatricopeptide repeat-containing protein 3, PTCD3), in the small subunit and MRPL59 (CR-6 interacting factor 1, CRIF1) in the large subunit. Furthermore, we have demonstrated the essential roles of CHCHD1, AURKAIP1, and CRIF1in mitochondrial protein synthesis by siRNA knock-down studies, which had significant effects on the expression of mitochondrially encoded proteins.

Requirement for CRIF1 in RNA interference and Dicer-2 stability

“…Indeed, many different functions have been reported for mammalian CRIF1, including functions as a transcription co-factor and functions in mitochondria. [29][30][31][32][33] We are currently investigating the functions of dCRIF and its role in Dcr-2 stability.…”

Mitochondrial Proteins Containing Coiled-Coil-Helix-Coiled-Coil-Helix (CHCH) Domains in Health and Disease

“…As a possibility, the expression 288 of COX2 could be low due to the decreased stability of CIV that results from nuclear DNA-289 encoded CIV subunits not being imported into the mitochondria. Alternatively, or in addition, 290 CHCHD4 might affect translation of COX2 via an indirect effect, through the regulation of 291 the import of its potential substrate CHCHD1 (Table 1), which is a component of the small 292 subunit of the mitochondrial ribosome [47,49,110]. The RNA-binding and (CX 9 C) 2 motif-293 carrying protein CHCHD1 is the mammalian homolog of yeast Mrp10 [47,49,111].…”

Assignment of 2′-O-Methyltransferases to Modification Sites on the Mammalian Mitochondrial Large Subunit 16 S Ribosomal RNA (rRNA)

“…Proteomics has identified a nearly complete set of mitochondrial ribosomal proteins (14 -21), some of which appear to be multifunctional (DAP3, AURKAIP, CRIF1, ICT1) (18,22,23). Our understanding of the mitoribosome structure is improving with advancements in cryo-EM technology (12, 24 -28), but the assembly process has received little attention.…”