Matthews C M, Trotman C N
Biochemistry Department, University of Otago, Box 56, Dunedin, New Zealand.
J Mol Evol. 1998 Dec;47(6):763-71. doi: 10.1007/pl00006435.
Artemia has evolved three distinct hemoglobins formed by the association of two nine-domain globin polymers. Sequence analysis of cDNA clones corresponding to two polymers, named T and C, indicates that their genes are the products of a duplication event some 60 million years ago. The present study indicates the presence of 22 introns in each of the T and C polymer genes. The 22 introns are classified into two groups: 17 correspond to positions within globin domains, and 5 correspond to interdomain linkers (or N- and C-terminal extensions). Intron position and reading frame phase are precisely conserved between T and C polymers for all 22 introns, but within each gene the position and phase are not always consistent from domain to domain or from linker to linker. The discordance of Artemia hemoglobin introns is discussed in terms of different model mechanisms and constraints: intron sliding, intron loss or gain, and the exon definition model of primary transcript RNA splicing. The results suggest that constraints of pre-mRNA processing should be considered when considering intron positional changes in homologous genes.
卤虫进化出了三种不同的血红蛋白，它们由两个九结构域的球蛋白聚合物结合而成。对对应于两种聚合物（分别命名为T和C）的cDNA克隆进行序列分析表明，它们的基因是约6000万年前一次复制事件的产物。本研究表明，T和C聚合物基因中各存在22个内含子。这22个内含子分为两组：17个对应于球蛋白结构域内的位置，5个对应于结构域间连接区（或N端和C端延伸区）。T和C聚合物的所有22个内含子在位置和阅读框相位上都精确保守，但在每个基因内，不同结构域之间或不同连接区之间的位置和相位并不总是一致的。本文从内含子滑动、内含子丢失或获得以及初级转录本RNA剪接的外显子定义模型等不同的模型机制和限制因素方面，对卤虫血红蛋白内含子的不一致性进行了讨论。结果表明，在考虑同源基因内含子位置变化时，应考虑前体mRNA加工的限制因素。
