在生物體中，蛋白質會彼此結合在一起，形成複合體，執行特殊的功能，這就是「蛋白質的交互作用」。hCDC5p是人類體內一個pre-mRNA剪接蛋白，它和出芽酵母菌(Saccharomyces cerevisiae) Ce1fp/Ntc85p 及 分裂酵母菌(Schizosaccharomyces pombe)CDC5p 的功能相似物。然而因為hCDC5p具有c-Myb DNA結合區，也可能是基因的轉錄因子，所以其轉錄因子的功能尚未被證實。因此我們透過酵母菌雙雜交系統(Yeast two-hybrid system)，從人類肝細胞基因庫中鑑定出與hCDC5p結合的相關蛋白C/EBPd。C/EBPd是屬於轉錄因子，在C端包括了一個高度保留性的basic leucine zipper domain，這個區域是負責形成雙體和結合至DNA。為了更進一步確實鑑定出這兩種蛋白交互作用的區域，我們將全長或不同片段的蛋白經酵母菌雙雜交系統觀察是否有相互作用的情形，但沒有發現hCDC5p和C/EBPd會互相結合的確切證據。可能的原因是當初篩選出的C/EBPd之C端序列融合了GAL4 activation domain形成了一個立體結構利於與hCDC5p相互作用，確實的原因並不清楚。在實驗過程中，我們再次驗證了C/EBPd的basic leucine zipper domain確實會與本身交互作用，且C/EBPd也會與HRAS1-reltated protein 的basic leucine zipper domain相互作用。此外，也發現hCDC5p的N端以及C端會啟動報導基因(reporter gene)，似乎有活化基因的效能， 所以我們推論hCDC5p的活化區域(transactivation domain)可能不只一個位置。 In organism, a protein can associate with another protein(s) to form a particular functional complex. This is designated" protein-protein interaction". Human hCDC5p is a human pre-mRNA splicing factor which is the homolog of.Saccharomyces cerevisiae Ce1fp/Ntc85p and Schizosaccharomycesupombe CDC5p.uBecause hCDC5p shares significant Myb DNA binding domainuof the vertebrate proto- oncoprotein c-Myb, hCDC5p may be. a putative transcription factor. Therefore, the hCDC5p maybe plays dual.functions. C/EBPd gene was isolated.from human liver cDNA library by yeast two-hybrid system and may interact with hCDC5p..C/EBPd is a transcription factor that contains a highly conserved basic leucine zipper.<a href="http://www.ntsearch.com/search.phpq=domain&v=56">domain</a> at the C-terminus that get involved in.dimerization and DNA binding..Full-length or truncated proteins of.hCDC5p and C/EBPd were used to examined whether they.interact with each other..Unfortunately, we had no strong evidences to prove that hCDC5p can associate.with C/EBPd. The possibility is.the chimeric structure of C-terminus of C/EBPd and a GAL4 activation <a href="http://www.ntsearch.com/search.phpq=domain&v=56">domain</a>.provides a favorable condition to interact with hCDC5p. We don’t known the actual reasons yet. The function of basic leucine zipper <a href="http://www.ntsearch.com/search.phpq=domain&v=56">domain</a> in C/EBPd.was confirmed to show the dimerization by yeast two-hybrid system. .In addition, .C/EBPd could associate with the leucine zipper.<a href="http://www.ntsearch.com/search.phpq=domain&v=56">domain</a> of HRAS1 related protein. The transactivation activities in both N-terminus.and C-terminus of hCDC5p were observed.indicating that hCDC5p probably contains more than one transactivation <a href="http://www.ntsearch.com/search.phpq=domain&v=56">domain</a>..
