The human mitochondrial translation initiation factor 2 gene ( MTIF2): transcriptional analysis and identification of a pseudogene

Abstract

Mitochondrial translation initiation factor 2 ( MTIF2) is nuclear-encoded and functions in mitochondria to initiate the translation of proteins encoded by the mitochondrial genome. To gain insight into mechanisms that regulate MTIF2 gene expression, the genomic copy and the 5′ and 3′ flanking regions of MTIF2 were isolated using a combination of genomic library screening and polymerase chain reaction (PCR). MTIF2 is ∼33.5-kb long and contains 16 exons, confirming data from the Human Genome Project. With RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE), we mapped the transcription start point in human heart tissue to a cytosine residue 296 bp upstream from the translation initiation site. The region surrounding the transcription start point contains consensus binding sites for transcription factors Sp1, nuclear respiratory factor 2 (NRF-2) and estrogen receptor, while enhancer binding sites were identified upstream. Promoter constructs were prepared in a luciferase reporter vector and transiently transfected into 293T cells. The minimal promoter gave an expression level 3.5× higher than the SV40 control ( P=0.001), while the construct containing the minimal promoter plus the enhancer region gave a 3.8× higher level of expression compared to the control ( P<0.001). We also discovered a pseudogene of MTIF2 and mapped it to chromosome 1p13-12.