COMPLEMENTARY DNAS FOR 2 ARYLAMINE N-ACETYLTRANSFERASES WITH IDENTICAL 5' NONCODING REGIONS FROM RAT PINEAL-GLAND

A cDNA library was constructed from the pineal gland of rats injected with isoproterenol and screened with P-32-labeled cDNAs encoding aryla mine N-acetyltransferases from rabbit and human liver. Two types of cD NAs for arylamine N-acetyltransferases (A-type and B-type) were isolat ed. Expression of the cDNAs in Chinese hamster ovary cells indicated t hat A-type N-acetyltransferase acetylates both aryl amines and arylalk ylamines, while the B-type enzyme acetylates only arylamines. Therefor e, neither the A-type nor the B-type of enzyme seems to be the arylalk ylamine N-acetyltransferase involved in melatonin synthesis in the pin eal gland. Nucleotide sequence analysis revealed that both A-type and B-type cDNAs code for 290 amino acids, and that they showed 82.8 % sim ilarity in the coding region. However, the nucleotide sequence in the 5' non-coding region was identical in the A-type and B-type cDNAs. In addition, the 5' non-coding region contained another possible open rea ding frame for 79 amino acids. Data base research revealed that the co mplementary sequence of the 5' non-coding region has high similarity w ith the coding regions of cDNAs for high-mobility-group proteins (HMG) 1 and 2, which are thought to regulate mRNA transcription.