Ichiyoshi Y, Endo H, Yamamoto M
Department of Biochemistry, Kyushu University, Fukuoka, Japan.
Biochim Biophys Acta. 1987 Oct 9;910(1):43-51. doi: 10.1016/0167-4781(87)90093-5.
We detected two size classes in rat liver alpha 2u-globulin mRNAs when analyzing cDNA clones, and named the mRNAs corresponding to the cDNA clones having longer and shorter sizes as L-type and S-type, respectively. When sequencing these cDNA clones, a 25 base insertion was present in the L-type at the 6th exon-intron junction. The extra sequence coincided with the 5' part of the reported 6th intronic sequence that is directly contiguous to the 3' part of the 6th exon. The relative abundance of L- and S-type mRNAs in the steady-state liver was determined by a sensitive S1 nuclease analysis using the probe prepared from the L-type cDNA. The same method was also applied for the determination of the L/S ratios during the course of postnatal development and estrogen treatment, all resulting in similar values, of about 0.03. These findings indicated that L-type and S-type mRNAs are generated by an alternative splicing mechanism in the 3' noncoding region of alpha 2u-globulin transcripts. Sequence analysis also elucidated the presence of at least two active genes showing exactly the same pattern of alternative splicing.
在分析大鼠肝脏α2u-球蛋白mRNA的cDNA克隆时，我们检测到了两种大小类型，并将对应较长和较短cDNA克隆的mRNA分别命名为L型和S型。对这些cDNA克隆进行测序时，L型在第6个外显子-内含子连接处存在一个25个碱基的插入。该额外序列与报道的第6个内含子序列的5'部分一致，该部分与第6个外显子的3'部分直接相邻。使用从L型cDNA制备的探针，通过灵敏的S1核酸酶分析确定了稳态肝脏中L型和S型mRNA的相对丰度。同样的方法也用于测定出生后发育过程中和雌激素处理期间的L/S比值，所有结果都相似，约为0.03。这些发现表明，L型和S型mRNA是由α2u-球蛋白转录本3'非编码区的可变剪接机制产生的。序列分析还阐明了至少两个活性基因的存在，它们显示出完全相同的可变剪接模式。
