The Partial CDNA Clone Of A Novel Member Of C/EBP Gene Family

We have obtained 9 positive clones by screening human placenta cDNA library with rat C/EBP cDNA probe. The largest clone HP8 contained 1844 base pairs which includes 496 coding base pairs. The matched DNA sequence has not been found in the GenBank (93.10,USA). The 165 amino acids encoded by this gene had the leucine zipper structure and demonstrated the highest homology (97%) with C/EBP throughout the DNA-binding domain and leucine repeat region (C-terminal 60 amino acids).Beyond this region,only low homology was detected in HP8 protein and C/EBP or C/EBP related proteins. Herewith, HP8 was defined a novel member of C/EBP gene family. Genomic Southern blot analysis confirmed that HP8 was a single copy gene. Northern blot analysis in 14 different fetus tissues showed that high level of HP8 mRNA was expressed in small intestine and skin, middle level in adrenal, low level in liver, lung, kidney, thyroid and gallbladder. In human adult liver tissue, low level HP8 mRNA was also found; whereas in 5 hepatoma and its surrounding nontumorous hepatic tissues, high level HP8 mRNA was detected in 2 hepatoma and one surrounding nontumorous hepatic tissue. These results suggested that the HP8 gene might be a transactivator related to cell growth. As Northern blot analysis indicated the HP8 gene had about 3. 0kb full length cDNA, the further cloning of 5' end of this cDNA is now in progress.