THE GENE AND PSEUDOGENES OF RAT S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE

Two rat liver genomic DNA libraries constructed in lambda DASH and lam bda Charon 4A were screened for sequences with similarity to S-adenosy l-L-homocysteine (AdoHcy) hydrolase cDNA. Of 36 clones purified, two c ontained the AdoHcy hydrolase gene sequence and 34 contained pseudogen e sequences. The AdoHcy hydrolase gene, which has been sequenced in it s entirety, spans approximately 15 kb and consists of 10 exons. Primer extension and S1 experiments show that transcription is initiated fro m two major initiation sites located at positions -63 and -62 from the starting codon and from several minor sites. The promoter region is l ocated in a CpG island, sequence TATTTAAA is present 23 bases upstream from the transcription start site, and an inverted CCAAT box is locat ed 285 bp upstream from the transcription start site. Other potential transcription-factor binding sites including SP1, AP-2, GRE and Oct-1 sites were identified in the 5'-flanking region. Several different pro cessed pseudogenes were found and analyzed.