APOLIPOPROTEIN A-1 OF JAPANESE-QUAIL - CDNA SEQUENCE AND MODULATION OF TISSUE EXPRESSION BY CHOLESTEROL FEEDING

Apolipoprotein (apo) A-1 cDNA was amplified by the reverse-transcripta se-polymerase chain reaction (RT-PCR). Primers were synthesized accord ing to the nucleotide sequence of chicken apo A-1, and the identity of apo A-1 cDNA was confirmed by comparing with the N-terminal amino aci d sequence. The open reading frame of apo A-1 cDNA consists of 795 nuc leotides, and it is capable of coding a polypeptide of 264 amino acids . A comparison between quail and chicken apo A-1 revealed 94.5% homolo gy in the nucleotide sequence and 91.7% homology in the amino acid seq uence, There was a similar 11- or 22-amino acid repeat in quail apo A- 1 as was the case for chicken apo A-1. Apo A-1 mRNA was evaluated to b e 1.4k in length and was expressed in various tissues of Japanese quai l: the liver, small intestine, lung, kidney, heart, and muscle, A quan titative evaluation, however, revealed that the liver and small intest ine were the major organs for apo A-1 synthesis, accounting for more t han 90% of the total expression of apo A-1 mRNA. Besides apo A-1 mRNA (1.4k in length), a transcript of 4.1k was detected in all the tissues examined, with a magnitude ranging from 5 to 10% of the apo A-1 mRNA level, The effect of cholesterol level on the expression of apo A-1 mR NA was studied to address the physiological significance of apo A-1 in the liver, small intestine, and muscle, The level of cholesterol in t he liver and breast muscle was increased by feeding with cholesterol a nd reached a saturation level at day 7. There was also a temporal rise of cholesterol level at day 7 in the small intestine, Dietary cholest erol increased the expression of apo A-1 mRNA two fold in both the liv er and small intestine, This was not the case for breast muscle, in wh ich the expression of apo A-1 mRNA was not modulated by the cholestero l level.