Multimerization of expressed protein-arginine methyltransferases during the growth and differentiation of rat liver
Multimerization of expressed protein-arginine methyltransferases during the growth and differentiation of rat liver
复制标题
DOI：
10.1016/j.bbagen.2005.02.015
复制
发表时间：
2005-05-25
影响因子：
3
通讯作者：
Kim, S
中科院分区：
文献类型：
--
作者：
Lim, Y;Kwon, YH;Kim, S
蛋白质精氨酸甲基化是一种翻译后修饰，在蛋白质中产生单甲基和二甲基（不对称或对称）精氨酸。我们研究了PRMT 1和PRMT 5在大鼠肝脏生长和分化过程中以及胰腺中的表达与其催化活性的关系。Western免疫印迹分析显示，PRMT 1和PRMT 5蛋白表达在肝和胰腺的细胞质中，分子量分别为约42 kDa和72 kDa。然而，在分子筛色谱上，酶活性在PRMT 5的约500 kDa和PRMT 1的约440 kDa处洗脱，表明这些表达的单体的多聚体复合物具有催化活性。而500 kDa的复合物甲基化主要髓鞘碱性蛋白（MBP），440 kDa的复合物甲基化hnRNP At蛋白。在胎鼠肝脏中，表达的42 kDa PRMT 1蛋白的量和甲基化hnRNP A1蛋白的酶活性分别比出生后肝脏高2- 3倍和4- 5倍。虽然72 kDa的PRMT 5蛋白被一致表达，但其活性仅变化约2倍。然而，PRMT 5甲基化MBP在出生后第20天左右显示出一个明显的峰值。此外，虽然PRMT 1酶活性在70%部分肝切除3天后增加超过10倍，但表达的PRMT 1蛋白质的量仅比对照肝脏高约3.2倍。总之，我们观察到PRMT仅以多聚体的形式具有催化活性，而不是作为表达亚基的二聚体或四聚体。此外，表达的PRMT蛋白的量，通过Western inummoblot测定，不相关的量的催化活性，因此，一些未表征的额外的因素可能多聚化PRMT表达催化活性在体内。(c)2005 Elsevier B. V.保留所有权利。
Protein-arginine methylation is a posttranslational modification which yields monomethyl and dimethyl (asymmetric or symmetric) arginines in proteins. We investigated the expressions of PRMT1 and PRMT5 in relation to their catalytic activities in rat liver during growth and differentiation as well as in the pancreas. Western immunoblot analysis revealed that both PRMT1 and PRMT5 proteins were expressed in the cytosol of liver and pancreas with molecular mass of about 42 kDa and 72 kDa, respectively. However, on molecular sieve chromatography, the enzyme activities were eluted at about 500 kDa for PRMT5 and 440 kDa for PRMT1, indicating that the multimer complex of these expressed monomers were catalytically active. While the 500 kDa complex methylated predominantly myelin basic protein (MBP), the 440 kDa complex methylated hnRNP At protein. In fetal rat liver, the amount of expressed 42 kDa PRMT1 protein and the enzyme activity to methylate hnRNP A1 protein were 2- to 3-fold and 4- to 5-fold higher, respectively, than those of post-natal livers. While the 72 kDa PRMT5 protein was consistently expressed, its activity varied only about 2-fold. However, PRMT5 to methylate MBP showed one distinct peak at around the 20th day post-natal. Furthermore, while the PRMT1 enzyme activity increased more than 10-fold after 3 days of 70% partial hepatectomy, the amount of expressed PRMT1 protein was only about 3.2-fold higher than the control livers. In summary, we observed that PRMTs are catalytically active only in the form of multimers, but not as a dimer or tetramer of the expressed subunit. Furthermore, the amount of expressed PRMT protein, determined by Western inummoblot, did not correlate with the amount of their catalytic activity, and thus, some uncharacterized additional factor(s) may multimerize PRMTs to express catalytic activities in vivo. (c) 2005 Elsevier B.V. All rights reserved.