Pryor Anne, Tung Luh, Yang Zhe, Kapadia Fehmida, Chang Tien-Hsien, Johnson Lee F
The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
Nucleic Acids Res. 2004 Mar 26;32(6):1857-65. doi: 10.1093/nar/gkh347. Print 2004.
URH49 is a mammalian protein that is 90% identical to the DExH/D box protein UAP56, an RNA helicase that is important for splicing and nuclear export of mRNA. Although Saccharomyces cerevisiae and Drosophila express only a single protein corresponding to UAP56, mRNAs encoding URH49 and UAP56 are both expressed in human and mouse cells. Both proteins interact with the mRNA export factor Aly and both are able to rescue the loss of Sub2p (the yeast homolog of UAP56), indicating that both proteins have similar functions. UAP56 mRNA is more abundant than URH49 mRNA in many tissues, although in testes URH49 mRNA is much more abundant. UAP56 and URH49 mRNAs are present at similar levels in proliferating cultured cells. However, when the cells enter quiescence, the URH49 mRNA level decreases 3-6-fold while the UAP56 mRNA level remains relatively constant. The amount of URH49 mRNA increases to the level found in proliferating cells within 5 h when quiescent cells are growth-stimulated or when protein synthesis is inhibited. URH49 mRNA is relatively unstable (T(1/2) = 4 h) in quiescent cells, but is stabilized immediately following growth stimulation or inhibition of protein synthesis. In contrast, there is much less change in the content or stability of UAP56 mRNA following growth stimulation. Our observations suggest that in mammalian cells, two UAP56-like RNA helicases are involved in splicing and nuclear export of mRNA. Differential expression of these helicases may lead to quantitative or qualitative changes in mRNA expression.
URH49是一种哺乳动物蛋白，与DExH/D盒蛋白UAP56有90%的同源性，UAP56是一种RNA解旋酶，对mRNA的剪接和核输出很重要。虽然酿酒酵母和果蝇只表达一种与UAP56相对应的蛋白，但编码URH49和UAP56的mRNA在人类和小鼠细胞中均有表达。这两种蛋白都与mRNA输出因子Aly相互作用，并且都能够挽救Sub2p（UAP56的酵母同源物）的缺失，这表明这两种蛋白具有相似的功能。在许多组织中，UAP56 mRNA比URH49 mRNA更丰富，不过在睾丸中URH49 mRNA要丰富得多。在增殖的培养细胞中，UAP56和URH49 mRNA的水平相似。然而，当细胞进入静止期时，URH49 mRNA水平下降3至6倍，而UAP56 mRNA水平保持相对稳定。当静止细胞受到生长刺激或蛋白质合成被抑制时，URH49 mRNA的量在5小时内增加到增殖细胞中的水平。在静止细胞中，URH49 mRNA相对不稳定（半衰期=4小时），但在生长刺激或蛋白质合成抑制后立即稳定。相比之下，生长刺激后UAP56 mRNA的含量或稳定性变化要小得多。我们的观察结果表明，在哺乳动物细胞中，两种类似UAP56的RNA解旋酶参与了mRNA的剪接和核输出。这些解旋酶的差异表达可能导致mRNA表达的定量或定性变化。
