牦牛、犏牛、藏黄牛和普通牛HIOMT基因CDS序列的比较

褪黑激素（MLT）是调控动物季节性生殖等多种生物节律,具有复杂生理功能的一种吲哚类激素,羟基吲哚-氧-甲基转移酶（hydroxyindole-O-methyltransferase,HIOMT）是决定MLT合成波动模式的重要酶之一。采用RT-PCR法克隆并分析了牦牛、犏牛和藏黄牛HIOMT基因的CDS序列。牦牛该基因序列连续缺失123bp,通过与普通牛基因组序列比对,该缺失片断位于HIOMT基因7个外显子中的第6外显子。由于克隆所得牦牛基因组DNA相应序列未缺失上述片断,推定所获得的牦牛HIOMT基因CDS序列属可变剪接体;克隆犏牛HIOMT基因获得长、短两条件序列,长序列与藏黄牛、普通牛该序列相似,短序列与牦牛相似,但尚不能确定这两条序列各自来自父本还是母本;与普通牛HIOMT基因比较,牦牛、犏牛和藏黄牛分别有11、13（长序列17）和11个变异位点,且位于密码子第1、2位点的变异分别为4、6（7）和4个,均为非同义突变,所有非同义突变只有1处由密码子第3位变异引起,这些突变可能通过影响蛋白结构进而影响其生物学功能。还预测了牦牛、犏牛、藏黄牛和普通牛HIOMT蛋白相对分子量、理论等电点、疏水性、跨膜区等。HIOMT的保守性较强,是系统进化研究较理想的分子标记。

Comparatioe Study on CDS sequence of HIOMI Gene among Yak,Cattle-yak,Tibetan-cattle and Cattle

Abstraet. Melatonin （MLT） was a kind of indoleamine hormone with complex physiological functions which can control the seasonal reproduction and other biological rhythm of animals, hydroxyindole-O- methyltransferase （HIOMT） was secreted rhythmicity and also one of the most important enzymes which can regulate the synthetic of MLT. RT-PCR was used in cloning the cattle yak, cattle-yak and Tibetan- cattle CDS of HIOMT and all the sequences were analyzed. A 123-bp deletion of this Gene was found in Yak, and this deletion was located at the 6th exon of all 7 exons of HIOMT gene compared with the Ge- nome sequence of cattle. Because this 123-bp fragment did not miss in the HIOMT gene sequences cloned from yak genome, this gene could be inferred as an alternative splicing of HIOMT gene of yak. Two se- quences of HIOMT gene of cattle-yak was cloned, the longer one was similar with Tibetan-cattle and cat- tle, and the shorter one was similar with yak, but it was still unknown who were the parents this two se- quences originated from. Compared with cattle HIOMT gene, there were 11, 13 （17 for long one） and 11 variation sites obtained between yak, cattle-yak and Tibetan-cattle, and 4, 6 （7） and 4 variation sites was located in 1st and 2nd codon respectively which was were all nonsynonymous mutations, only 1 nonsynon- ymous mutation was caused by variation sites which located in 3rd codon, all those nonsynonymous muta- tions could cause the change of protein structure to affect the biological function of this gene. The MW, pI, hydrophobicity, transmembrance region and other protein characters were also predicted. The highly conserved sHIOMT gene also indicated that this gene might be a more ideal genetic marker in the studies of systematic and evolutionary.