探討以光線對光反應基因中的光反應片段作活化之可能機制

在已知光反應基因的啟動子(promoters)內，都存在著光反應片段(light-responsive elements, LREs)。亦即，當光線對LREs產生影響時，該基因就開始被活化以產生相關的蛋白質。到目前為止，在生物的基因中已經有許多不同LREs被發現，例如一般較熟悉的植物基因中的 G-box和動物生理時鐘基因內的E-box等皆是。顯而易見的，這其中光反應基因的活化關鍵在於“光線如何對LREs進行影響，以致於改變基因的轉錄活性〞。然而，這個部份至今尚無明確、嚴謹的定論。依現行理論的說法，在光誘導的生化反應途徑中，都會有一個最初的光受體(photoreceptors)存在，這個光受體的作用是將光訊號轉換成化學訊息，再透由化學訊息產生後續的反應，因而反應的過程中光線只會出現在最初的光受體誘導過程中。但光線是否也可能參與了後續的調控動作，甚至是扮演著後續蛋白質合成的關鍵角色？這也許是極有可能的，因為從鹼基的吸收光譜和非線性光學效應去推測，DNA的分子結構會因為吸收光線而觸發產生不同的激發狀態，所以不同的光線經過干涉後照射到特定的調控序列(motif)或啟動子序列(promoter)後，會因為生物體本身的非線性引致調控序列的能量狀態改變，進而使得該序列下游的基因發生轉錄活性的變化。吾人在比對不同的光反應片段的鹼基機率分佈曲線和干涉光所對應的鹼基吸光曲線之後發現兩者具有相同的趨勢。這表示不同的干涉光所對應的鹼基吸光或然率和其特定序列的鹼基機率分佈之間具有幾近一致的相關性。或許，一個蛋白質的被選定與合成並非基於某種決定論（deterministic）的程序，而反而可能是透由數次試誤過程，終至達成啟動目的的統計式（statistical）途徑。此研究計畫係在虎科大光電同調控制實驗室與奧博實驗室之全力支援下進行。

關鍵字

啟動子；光反應片段；干涉；機率分佈；去氧核醣核酸

並列摘要

A gene expression is generally believed to be singled out from within the large chromosome pool once its corresponding promoter is activated by some means. It is suspected that light interference may play an essential role in pulling this trigger. In fact, all known light-responsive promoters thus far are concluded, within our lab, to be activated in a more-or-less unintended statistical sampling fashion, rather than in a deterministic precise manner. It is thus argued that the known population distribution of base pairs A, T, G, C, within a specific promoter can always be matched by the so-called activation probability distribution deduced from a weight-summed light absorption tendencies of each DNA base pair on photons generated by interference of UV, VIS, and IR lights within a nonlinear bio-system. In other words, such statistical means of promoter sampling/triggering does not guarantee the offering of correct promoter sequence ordering each time. Nonetheless, owing to the typically small number of base pairs (of about 6-10) within a promoter, in principle it does not take long to reach the eventual matching ordering after several trials. Subsequently, the corresponding mRNA is transcribed and then the specific protein generated. Examples demonstrating such gene expression scheme are provided, even though the underlying physical processes connecting light absorption and promoter activation remain largely unknown.

並列關鍵字

promoters ； light-responsive elements, LREs ； interference ； probability distribution ； DNA

參考文獻

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探討以光線對光反應基因中的光反應片段作活化之可能機制

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