Grève P, Voisin P, Grechez-Cassiau A, Bernard M, Collin J P, Guerlotté J
Laboratoire de Neurobiologie Cellulaire, URA CNRS 1869, Poitiers, France.
Biochem J. 1996 Nov 1;319 ( Pt 3)(Pt 3):761-6. doi: 10.1042/bj3190761.
The production of the pineal hormone melatonin displays circadian variations with high levels at night. The last enzyme involved in melatonin biosynthesis is hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4). The expression of the mRNA encoding chicken HIOMT was investigated in vivo and in vitro throughout the light/dark cycle, in constant darkness and with light interruption of the dark phase. The stability of HIOMT mRNA was also examined. A day/night rhythm of HIOMT mRNA levels, with a peak at the midlight phase, was observed in vivo as well as in vitro. Constant darkness did not abolish this rhythm in vivo. One cycle of the HIOMT mRNA rhythm could be observed in constant darkness in vitro. In addition, a stimulatory effect of light on HIOMT mRNA levels during the dark phase could be observed in vivo as well as in vitro. HIOMT mRNA stability was not affected by light or dark conditions, as demonstrated by chase experiments with actinomycin D. The results indicate that the daily changes in HIOMT mRNA concentration reflect transcriptional regulation by circadian oscillators and photosensory mechanisms that are endogenous to the pineal gland.
松果体激素褪黑素的分泌呈现出昼夜变化,夜间水平较高。参与褪黑素生物合成的最后一种酶是羟吲哚 - O - 甲基转移酶(HIOMT,EC 2.1.1.4)。在整个光/暗周期、持续黑暗以及暗期有光照中断的情况下,对编码鸡HIOMT的mRNA表达进行了体内和体外研究。还检测了HIOMT mRNA的稳定性。在体内和体外均观察到HIOMT mRNA水平的昼夜节律,在光照中期达到峰值。持续黑暗并未消除体内的这种节律。在体外持续黑暗条件下可观察到HIOMT mRNA节律的一个周期。此外,在体内和体外均可观察到暗期光照对HIOMT mRNA水平有刺激作用。如用放线菌素D进行追踪实验所示,HIOMT mRNA稳定性不受光照或黑暗条件影响。结果表明,HIOMT mRNA浓度的每日变化反映了松果体内源性昼夜振荡器和光感机制的转录调控。