Seeking Common Ground in Nuclear Complexity
نویسندگان
چکیده
On a molecular scale, the nucleus is a big place. And, due to the enormous mass of DNA, RNA, and protein concentrated there, the nucleus is far denser than the cytoplasm. So the question of how various nuclear factors move about and efficiently find their sites of action has long been a subject of interest and debate. This biological problem is complicated by the fact that most such factors function in large macro-molecular assemblies, with as many as 100 components that must interact at the right time and place. Relevant to this, many factors, including splicing factors, are both dispersed through the nucleoplasm and concentrated in certain nuclear compartments (Fig. 1). Two recent studies, one in The Journal of Cell Biology (Kruhlak et al., 2000) and the other in Nature (Phair and Misteli, 2000) provide new insights into this fundamental question. Both studies investigate the nuclear dynamics of green fluorescent protein (GFP) 1 –labeled proteins, particularly splicing factor ASF/SF2, in living cells using FRAP (fluorescence recovery after photobleaching) and FLIP (fluorescence loss in photobleaching) to ask the question: how fast do splicing factors move within the nucleus? The answer to this question is significant for understanding the mechanisms by which nuclear factors reach their sites of function. Do the kinetics of factor movement suggest that they are freely diffusing or constrained by structure, perhaps actively recruited from one place to the next? Is ASF/ SF2 in the dispersed nucleoplasmic pool, thought to be the most active fraction, more mobile than in the highly concentrated regions frequently considered to be factor storage sites?
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عنوان ژورنال:
- The Journal of Cell Biology
دوره 150 شماره
صفحات -
تاریخ انتشار 2000