Oku H, Toda T, Nagata J, Ishikawa M, Neyazaki K, Shinjyo C, Chinen I
Laboratory of Applied Biochemistry, Faculty of Agriculture, University of The Ryukyus, Okinawa, Japan.
Biosci Biotechnol Biochem. 1997 Feb;61(2):286-90. doi: 10.1271/bbb.61.286.
Apolipoprotein (apo) A-1 cDNA was amplified by the reverse-transcriptase-polymerase chain reaction (RT-PCR). Primers were synthesized according 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 acid sequence. The open reading frame of apo A-1 cDNA consists of 795 nucleotides, and it is capable of coding a polypeptide of 264 amino acids. A comparison between quail and chicken apo A-1 revealed 94.5% homology in the nucleotide sequence and 91.7% homology in the amino acid sequence. 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 be 1.4 k in length and was expressed in various tissues of Japanese quail: the liver, small intestine, lung, kidney, heart, and muscle. A quantitative evaluation, however, revealed that the liver and small intestine were the major organs for apo A-1 synthesis, accounting for more than 90% of the total expression of apo A-1 mRNA. Besides apo A-1 mRNA (1.4 k in length), a transcript of 4.1 k 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 mRNA was studied to address the physiological significance of apo A-1 in the liver, small intestine, and muscle. The level of cholesterol in the liver and breast muscle was increased by feeding with cholesterol and reached a saturation level at day 7. There was also a temporal rise of cholesterol level at day 7 in the small intestine. Dietary cholesterol increased the expression of apo A-1 mRNA two fold in both the liver and small intestine. This was not the case for breast muscle, in which the expression of apo A-1 mRNA was not modulated by the cholesterol level.
通过逆转录聚合酶链反应（RT-PCR）扩增载脂蛋白（apo）A-1 cDNA。根据鸡apo A-1的核苷酸序列合成引物，并通过与N端氨基酸序列比较来确认apo A-1 cDNA的一致性。apo A-1 cDNA的开放阅读框由795个核苷酸组成，能够编码一个264个氨基酸的多肽。鹌鹑和鸡apo A-1之间的核苷酸序列同源性为94.5%，氨基酸序列同源性为91.7%。鹌鹑apo A-1中存在与鸡apo A-1类似的11或22个氨基酸的重复序列。评估apo A-1 mRNA的长度为1.4 kb，并在日本鹌鹑的各种组织中表达：肝脏、小肠、肺、肾、心脏和肌肉。然而，定量评估显示肝脏和小肠是apo A-1合成的主要器官，占apo A-1 mRNA总表达量的90%以上。除了长度为1.4 kb的apo A-1 mRNA外，在所有检测的组织中还检测到一个4.1 kb的转录本，其大小为apo A-1 mRNA水平的5%至10%。研究了胆固醇水平对apo A-1 mRNA表达的影响，以探讨apo A-1在肝脏、小肠和肌肉中的生理意义。通过喂食胆固醇增加肝脏和胸肌中的胆固醇水平，并在第7天达到饱和水平。小肠中胆固醇水平在第7天也有暂时升高。饮食中的胆固醇使肝脏和小肠中apo A-1 mRNA的表达增加了两倍。胸肌则不然，其中apo A-1 mRNA的表达不受胆固醇水平的调节。
