Boeck R, Tarun S, Rieger M, Deardorff J A, Müller-Auer S, Sachs A B
Department of Molecular and Cell Biology, University of California at Berkeley 94720, USA.
J Biol Chem. 1996 Jan 5;271(1):432-8. doi: 10.1074/jbc.271.1.432.
The removal of the mRNA poly(A) tail in the yeast Saccharomyces cerevisiae is stimulated by the poly(A)-binding protein (Pab1p). A large scale purification of the Pab1p-stimulated poly(A) ribonuclease (PAN) identifies a 76-kDa and two 135-Da polypeptides as candidate enzyme subunits. Antibodies against the Pan1p protein, which is the minor 135-kDa protein in the preparation, can immunodeplete Pan1p but not PAN activity. The protein sequence of the major 135-kDa protein, Pan2p, reveals a novel protein that was also found in the previously reported PAN purification (Sachs, A. B., and Deardorff, J. A. (1992) Cell 70, 961-973). Deletion of the non-essential PAN2 gene results in an increase of the average length of mRNA poly(A) tails in vivo, and a loss of Pab1p-stimulated PAN activity in crude extracts. These data confirm that Pan2p and not Pan1p is required for PAN activity, and they suggest that ribonucleases other than the Pab1p-stimulated PAN are capable of shortening poly(A) tails in vivo.
在酿酒酵母中，聚腺苷酸结合蛋白（Pab1p）可刺激mRNA聚腺苷酸尾巴的去除。对受Pab1p刺激的聚腺苷酸核糖核酸酶（PAN）进行大规模纯化，鉴定出一个76 kDa的多肽和两个135 Da的多肽作为候选酶亚基。针对制备物中较小的135 kDa蛋白Pan1p的抗体，可免疫去除Pan1p，但不能去除PAN活性。主要的135 kDa蛋白Pan2p的蛋白质序列揭示了一种新蛋白，该蛋白也在先前报道的PAN纯化中被发现（萨克斯，A. B.，和迪尔多夫，J. A.（1992年）《细胞》70卷，961 - 973页）。缺失非必需的PAN2基因会导致体内mRNA聚腺苷酸尾巴平均长度增加，以及粗提物中Pab1p刺激的PAN活性丧失。这些数据证实PAN活性需要Pan2p而非Pan1p，并且表明除Pab1p刺激的PAN之外的核糖核酸酶也能够在体内缩短聚腺苷酸尾巴。
