Dynamic association of RNA-editing enzymes with the nucleolus
Dynamic association of RNA-editing enzymes with the nucleolus
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DOI：
10.1242/jcs.00371
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发表时间：
2003-05-01
影响因子：
4
通讯作者：
Carmo-Fonseca, M
中科院分区：
文献类型：
--
作者：
Desterro, JMP;Keegan, LR;Carmo-Fonseca, M
ADAR 1和ADAR 2是在长双链RNA双链体和特异性前mRNA转录物中将腺苷脱氨基为肌苷的编辑酶。在这里，我们表明，全长和N-末端截短形式的ADAR 1同时表达在HeLa和COS 7细胞由于使用替代起始蛋氨酸。由于ADAR 1的N-末端含有核输出信号，全长蛋白主要定位于细胞质中，而N-末端截短形式仅在核中并在核仁中积累。ADAR 2缺乏与ADAR 1的N-末端结构域同源的区域，仅定位于细胞核，并且类似地在核仁中积累。在核仁内，ADAR 1和ADAR 2共定位在一个新的隔室中。光漂白实验表明，在活细胞中，ADAR 1和ADAR 2是在恒定的流量进出核仁。当细胞表达有编辑能力的谷氨酸受体GluR-B RNA时，内源性ADAR 1和ADAR 2从核仁去定位并在底物转录物积累的位点积累。这表明ADAR 1和ADAR 2不断地通过核仁移动，并可能被募集到细胞中其他地方的特定编辑底物上。
ADAR1 and ADAR2 are editing enzymes that deaminate adenosine to inosine in long double stranded RNA duplexes and specific pre-mRNA transcripts. Here, we show that full-length and N-terminally truncated forms of ADAR1 are simultaneously expressed in HeLa and COS7 cells owing to the usage of alternative starting methionines. Because the N-terminus of ADAR1 contains a nuclear export signal, the full-length protein localizes predominantly in the cytoplasm, whereas the N-terminally truncated forms are exclusively nuclear and accumulate in the nucleolus. ADAR2, which lacks a region homologous to the N-terminal domain of ADAR1, localizes exclusively to the nucleus and similarly accumulates in the nucleolus. Within the nucleolus, ADAR1 and ADAR2 co-localize in a novel compartment. Photobleaching experiments demonstrate that, in live cells, ADAR1 and ADAR2 are in constant flux in and out of the nucleolus. When cells express the editing-competent glutamate receptor GluR-B RNA, endogenous ADAR1 and ADAR2 de-localize from the nucleolus and accumulate at sites where the substrate transcripts accumulate. This suggests that ADAR1 and ADAR2 are constantly moving through the nucleolus and might be recruited onto specific editing substrates present elsewhere in the cell.