Godiska R, Yao M C
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Cell. 1990 Jun 29;61(7):1237-46. doi: 10.1016/0092-8674(90)90688-b.
During macronuclear development in ciliates, precise deletion events eliminate thousands of specific DNA segments. Each segment is bounded by a unique pair of short direct repeats, but no other common feature has been reported. To determine the critical cis-acting sequences, we developed an in vivo system for analyzing this process in Tetrahymena. We show that sequences essential for recognition and excision of one such region are located within the 70 bp of DNA flanking either side of it. Three authentic splice sites and one cryptic site are each adjacent to an unusual polypurine tract (5'-A5G5) situated 40-50 bp distal to each terminal repeat. Removal of this tract or substitution of 3 bp within it abolishes splicing to the adjacent site. The normal chromosomal environment and the integrity of the eliminated sequence are not required for its removal. We believe the polypurine tract is a signal essential for excision of this sequence.
在纤毛虫的大核发育过程中，精确的缺失事件会消除数千个特定的DNA片段。每个片段都由一对独特的短正向重复序列界定，但尚未报道其他共同特征。为了确定关键的顺式作用序列，我们开发了一种在体内分析嗜热四膜虫这一过程的系统。我们发现，识别和切除一个这样的区域所必需的序列位于其两侧侧翼70 bp的DNA范围内。三个真实的剪接位点和一个隐蔽位点分别与一个不寻常的多聚嘌呤序列（5'-A5G5）相邻，该序列位于每个末端重复序列远端40-50 bp处。去除该序列或替换其中3个碱基会消除与相邻位点的剪接。该序列的去除不需要正常的染色体环境和被消除序列的完整性。我们认为多聚嘌呤序列是切除该序列所必需的信号。
