Study On The Function Of Mitochondrial Translation Initiation Factors Mti2 And Mti3 In Schizosaccharomyces Pombe

Mitochondria is an organelle commonly found in eukaryotes.It not only involved in the synthesis of ATP,but also in the physiological processes such as cellular metabolism and apoptosis.A majority of mitochondrial diseases are caused by the impaired mitochondrial function,so mitochondria is closely related to human health.Schizosaccharomyces pombe is closer to human than other species in evolution,so it is an excellent mode organism for studying mitochondrial function.Nowdays mitochondria is becoming more and more popular with researchers.The mitochondria have its own genome but can only synthesize small amounts of protein.The fission yeast mitochondrial genome encodes 25 kinds of tRNAs,2 kinds of rRNAs,a RNase P RNA and 7 kinds of mitochondrial respiratory chain complex subunits,including the Gob1 subunit of complex ?,three large subunits of complex?(Cox1,Cox2,Cox3),three subunits of complex ?(Atp6,Atp8,Atp9)and the ribosomal protein(Varl).The protein translation requires the initiation factor,elongation factor and termination factor to participate in regulation.The pombase database of S.pombe predicts that Mti2 and Mti3 protein are involved in translation initiation of mitochondria protein.The discovery of Mti2 was due to the interaction between Ppr 10 and Mti2 in the previous experimental co-immunoprecipitation.Therefore,this article mainly explores the main function of Mti2,Mti3 in S.pombe.First,we constructed mti2 and mti3 gene deletion strain,it was found that the loss of mti2 showed growth defects on a non-fermented medium with glycerol as the sole carbon source.This suggests that the loss of mti2 gene impares the function of the mitochondrial respiratory chain,whereas the loss of mti3 did not impair mitochondrial respiratory function.Second,by changing the culture temperature and the incubation time,it was investigated that the cells of Amti2 strain had a some death in the late stage of the stationary phase and the Amti2 strain was more severely inhibited at 37 ?.Third,it was initially confimed that the translation initiation factor IFM1 protein in the Saccharomyces cerevisiae was able to rescue the Amti2 strain,indicating that IFM1 protein and Mti2 protein have functional conservation.Then,real-time quantitative PCR revealed that the loss of mti2 gene affected the mRNA level encoded by the mitochondrial genome and decreased the mitochondrial genome copy numbers in the late stage of the stationary phase.Finally,BN-PAGE and Western blot experiments showed that the loss of mti2 gene severely affected the assemble of mitochondria complexs and supercomplexs.The experimental result indicates that the Mti2 protein plays a crucial role in fission yeast.