Gao F, Endo H, Yamamoto M
Department of Biochemistry, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Nucleic Acids Res. 1989 Jun 26;17(12):4629-36. doi: 10.1093/nar/17.12.4629.
Rat alpha 2 mu globulins are coded for by a family of about 25 structurally related genes, some of which are expressed in the male adult liver while the other subset seems to be active in several excretory organs, including salivary and lacrymal glands. To estimate the number and specificity of genes expressed in the salivary glands, we determined nucleotide sequences of 30 cDNA clones. At least two alpha 2 mu globulin genes are active and two thirds of mRNAs were shown to code for the peptide two amino acids shorter than the others. Unexpected observation was the intense length polymorphism in the 3' non-coding 6th intron-7th exon regions presumably caused by alternative splice-acceptor selection. At least six acceptor sites were utilized and the longest type retained the entire 6th intronic sequence resulting in a formation of unusually longer product. A stable mRNA molecule of this type was demonstrated in salivary glands by Northern blotting probed with the 6th intron-specific fragment. Together with three independent polyadenylation sites, the rat salivary glands generate a diverse set of alpha 2 mu globulin mRNAs.
大鼠α2μ球蛋白由一个约25个结构相关基因的家族编码，其中一些基因在成年雄性肝脏中表达，而另一部分似乎在包括唾液腺和泪腺在内的几个排泄器官中活跃。为了估计唾液腺中表达的基因数量和特异性，我们测定了30个cDNA克隆的核苷酸序列。至少有两个α2μ球蛋白基因是活跃的，并且三分之二的mRNA编码的肽比其他肽短两个氨基酸。意外的发现是在3'非编码第6内含子-第7外显子区域存在强烈的长度多态性，这可能是由可变剪接受体位点选择引起的。至少利用了六个受体位点，最长的类型保留了整个第6内含子序列，导致形成异常长的产物。通过用第6内含子特异性片段进行Northern印迹分析，在唾液腺中证实了这种类型的稳定mRNA分子。大鼠唾液腺与三个独立的聚腺苷酸化位点一起，产生了一组多样的α2μ球蛋白mRNA。
