Bosch M, Cayla X, Van Hoof C, Hemmings B A, Ozon R, Merlevede W, Goris J
Afdeling Biochemie, Katholieke Universiteit Leuven, Belgium.
Eur J Biochem. 1995 Jun 15;230(3):1037-45. doi: 10.1111/j.1432-1033.1995.tb20653.x.
cDNA clones encoding the 65-kDa (PR65) and 55-kDa (PR55) regulatory subunits of protein phosphatase 2A from Xenopus laevis were isolated by homology screening with the corresponding human cDNAs, and used to analyze the developmental expression patterns of these genes. The PR65 subunit was found to be encoded by two genes, termed XPR65 alpha and XPR65 beta. The open reading frames of the alpha and beta cDNAs both span 1767 bp, and predict proteins of 64.4 kDa and 65.3 kDa, respectively, that are 87% identical. The predicted amino acid sequence of XPR65 alpha showed 95% and 84% identity with human PR65 alpha and PR65 beta proteins, respectively, whereas the identity of XPR65 beta with the same proteins was 87% and 86.5%, respectively. Only one type of Xenopus PR55 (XPR55) was isolated that showed 93% and 84% similarity to human PR55 alpha and PR55 beta, respectively. Analysis of the N-terminal region of XPR55 with the same regions of human PR55 alpha and PR55 beta, indicates that the XPR55 is the Xenopus homolog of the human PR55 alpha isoform. Despite the overall similarity with PR55 from other species, XPR55 has an N-terminal extention of at least 24 amino acids. In the ovary, a transcript of 2.8 kb, encoding the XPR65 beta, was predominantly expressed and these XPR65 beta mRNAs are present at a constant level during oogenesis until late embryogenesis. Expression of the 2.4-kb XPR65 alpha was low until the larval stage, then dramatically increased. In all adult tissues except ovary, the 2.4-kb alpha-specific mRNA was more abundant than the 2.8-kb beta transcript. Two transcripts of 2.4 kb and 2.5 kb, encoding the XPR55 subunit, were detected at a constant level throughout Xenopus oogenesis and during embryogenesis. Both transcripts were also expressed at similar levels in all adult tissues, but in a tissue-specific manner. Analysis of the XPR55 and XPR65 proteins using antibodies to recombinant proteins revealed that the overall levels of the two proteins were constant, in good agreement with mRNA data.
通过与人相应的cDNA进行同源性筛选，分离出了编码非洲爪蟾蛋白磷酸酶2A的65 kDa（PR65）和55 kDa（PR55）调节亚基的cDNA克隆，并用于分析这些基因的发育表达模式。发现PR65亚基由两个基因编码，分别称为XPR65α和XPR6 5β。α和β cDNA的开放阅读框均跨越1767 bp，分别预测编码64.4 kDa和65.3 kDa的蛋白质，二者的同一性为87%。XPR65α的预测氨基酸序列与人类PR65α和PR65β蛋白的同一性分别为95%和84%，而XPR65β与相同蛋白的同一性分别为87%和86.5%。仅分离出一种非洲爪蟾PR55（XPR55），它与人类PR55α和PR55β的相似性分别为93%和84%。对XPR55的N端区域与人类PR55α和PR55β的相同区域进行分析表明，XPR55是人类PR55α亚型的非洲爪蟾同源物。尽管与其他物种的PR55总体相似，但XPR55具有至少24个氨基酸的N端延伸。在卵巢中，编码XPR65β的2.8 kb转录本占主导表达，并且这些XPR65β mRNA在卵子发生直至胚胎发育后期均以恒定水平存在。2.4 kb的XPR65α的表达在幼体阶段之前较低，然后急剧增加。在除卵巢外的所有成体组织中，2.4 kb的α特异性mRNA比2.8 kb的β转录本更丰富。在非洲爪蟾整个卵子发生过程和胚胎发育过程中，检测到编码XPR55亚基的2.4 kb和2.5 kb的两种转录本，其水平恒定。这两种转录本在所有成体组织中也以相似水平表达，但具有组织特异性。使用针对重组蛋白的抗体对XPR55和XPR65蛋白进行分析表明，这两种蛋白的总体水平恒定，与mRNA数据高度一致。
