| Introduction:Rapid Amplification of cDNA Ends ( RACE ) is a PCR - based method by which the full 5' and 3' end of cDNA could be got through the known part of that cDNA. It is simpler and more rapid and a necessary tool for getting the full length cDNA compared to genome researching. We can get more information in a shorter period by studying cDNA. Also it is a simple and effective method and can conduct amplification in low abundance transcript rapidly, it is superior to the classical method of library construction and screening and has become an indispensable tool for genome research. With the completion of Human Genome Project, the human genetic code is no longer a secret. The main task is to locate the nearly 30,000 genes encoding human diverse proteins on the exact site of chromosome. Based on such an object, RACE, as a simple and effective tool for novel gene cloning, is taken more and more accountance to. In our study, we get a full -length cDNA from human liver marathon cDNA library by means of RACE on the base of former research work in exon trapping. After searching in GenBank of NCBI, we found it is a novel gene encodinghuman alpha - 1 - B glycoprotein ( GenBank Accession number : AF414429) , which is a new member of immunoglobulin superfamily. Materials :1. Human liver Marathon - Ready cDNA2. Molecular Biology Reagents for Gene Cloning.3. Reagents for Northern Blot and RT - PCR4. Various fetus tissues Methods:5' - GSP and 3' - GSP was designed according to exon sequence acquired by means of exon trapping technique. We can get the corresponding 5' - RACE and 3' - RACE fragment by amplifying the Liver Marathon cDNA library using PCR technique. Then we explore the gene expression pattern in various human tissues by Northern Blot and RT - PCR using probe or gene specific primers designed according to the 3'- RACE fragment.Results:Using the RACE method, we got a 5' - RACE product of 450bp and a 3' - RACE product of 1650bp. The RACE products were purified and subcloned into a pMD - 18 vector before being sequenced. After removing the overlapping part of these two fragments, a full -length cDNA of 1694bp was spliced. Using the ORF of NCBI, we can see that the 43 - 1530 nt is a complete open reading frame, among which the 1 -51nt encodes a signal peptide. Search at GenBank of NCBI shows that it is a novel gene ( GenBank Submission No. AF414429) with a coding region of 1482nt,encoding a protein of 495 amino acids. Homology search at Translated Blast Search of NCBI suggests that it is alpha - 1 - B glycoprotein Precursor Gene. Northern Blot and RT - PCR analysis demonstrated that it is expressed in sever-al human tissues with the highest expression in fetus liver.Discussion:Alpha - IB - glycoprotein is present in normal adult plasma at an average concentration of 22 mg/dl. The complete amino acid sequence of alpha -IB glycoprotein, a plasma protein of unknown function, has been determined for more than fifteen years. Yet its corresponding cD-NA was not identified up till now. In our study, a full - lengh cDNA encoding alpha -IB glycoprotein was successfully identified from human liver cDNA library by means of RACE. Also we studied its expression pattern in various human tissues by Northern Blot and RT -PCR. The gene is 1694bp in length with a 1482 nt open reading frame, encoding a protein of 495 amino acids. The encoded protein consists of a signal peptide and four IGc2 domains, so was classified as a novel member of immunoglobulin superfamily. There are many members in the superfamily of immunoglobulin, most of which are involved in the process of immune response or cell growth, such as leucocyte - function associated antigen, platelet - derived growth factor receptor, neural cell adhesion molecule, et. They all have IG - like domain which can interact with other domains in the form of homophil-ic and heterophilic manner. So we deduced that alpha - 1 - B glycoprotein may act as a " bridge" in the interaction of protein and protein, protein and ligand thr...
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