哺乳类心脏肌浆球蛋白重链基因中的富嘧啶基内含子的唯一保守性

研究了人类和大鼠的心脏α和β-肌球蛋白重链基因中的嘧啶基比例。编码MyHC尾的外显子均是缺少嘧啶基的。这一特殊发现，即某些内含子是富嘧啶基的，而此种富嘧啶基状态在人类和大鼠均有保留，使所有四种等位基因共有两个富含嘧啶基的内因子，并且每对标准基因均含有两种不同的富含嘧啶基内因子。此种强烈保守性与这些内含子的序列无关。基于基因组序列的对比研究所得到的上述发现提示基因组序列除了编码心脏肌球蛋白重链多肽的作用以外，还具有其他附加的功能。

A unique conservation of the pyrimidine-rich introns in the mammalian cardiac myosin heavy chain genes

The pyrimidine ratio of the cardiac α -and β-myosin heavy chain gene s from human and the Syrian hamster was studied.Exons coding for the MyHC tail w ere uniformly pyrimidine-poor (36.72%)，due to the coding for large numbe r of amino acid residues with low or no pyrimidines.The puzzling finding was that som e introns were purimidine-rich(CT-rich)and the CT-richnesses were conserved i n b oth the Syrian hamster and human,with all the four isogenes sharing two CT-ric h introns and each pair of orthologous genes having another two distinctive sets o f CT-rich introns.The strong conservation of the CT-richness was independent of the sequences of these introns,which were poorly conserved.In addition,regardles s of the probable strand-asymmetry brought forth by the CT-richness,these intr ons were not involved in any detectable genomic recombination events,indicating existence of evolutionary constraints.This novel finding based on the comparison of the genomic sequences indicates additional functions of the genomic sequence besides the coding for cardiac myosin heavy chain polypeptides.