Encoding Endoplasmic Reticulum Membrane Protein Gene Hrtn3 And Its Mouse Homologue Gene Mrtn3 Cloning And Functional Studies

It's known that the secret of proteins is consisted of a serious of intricate courses. In brief, protein is synthesized in ribosome on the rough ER, followed by transport through ER, then is selectively sorted to different sub-cell organelles including the Golgi apparatus, endosomes, lysosomes or secretary vesicles. Among them, the membrane of ER plays an important role. Additionally, during the secret of the new synthesized proteins, most proteins were subjected to various process of post translational modification. It has been reported that this kind of modification may already begin in ER. In recently years, some studies showed that the different protein on the membrane of ER, which have their different expression pattern in tissues or cells, could transport some specific kinds of proteins to the sub-cell organelles such as the Golgi apparatus. At the same time, the proteins belonging to the RTN family, which are also the important proteins localized on the membrane of ER, have been revealed to be associate to the differentiation, the apoptosis and the regeneration of axons. During screening of the arrayed human fetal brain and mouse cDNA libraries, two cDNA clones, hRTN3 and mRTN3 were obtained and these genes belonged to the RTN family.According to the EST we had obtained (AF072813), whose homologues in human had high expression pattern in brain, we got the template of the probe to screen the arrayed human brain cDNA library. Through hybridization screening twice, we identified the positive cDNA clone (GenBank accession number is AF119297). The full length of hRTN3 was 2559bp, containing an open reading frame encoding 235 amino acids. The ATG at the position of 137-139 was predicted as the initiation codon because there is an in-frame upstream stop codon at nt 44-46 and the sequence around the potential translation initiation conformed well to the consensus sequence of Kozat. Additionally, using Gapped BLASTn program we searched the nucleic acids of hRTN3 that was not well homologious to NSP-A, NSP-B, NSP-C ,while the peptides is highly homologous to them, especially in carboxyl-terminal. At the same time, there were two large hydrophobic regions in this segment, which had been confirmed to play an important role in the interaction between the proteins and the membrane of endoplasm reticulum. Further analysis revealed that the amino-terminal residues were specific and were rich of serine, which could be potential phosphorylation sites. The other positive cDNA clone from mouse brain library, mRNT3, was 2814bp. Its open reading frame encoded a 237 amino...