Misquitta C M, Sing A, Grover A K
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Biochem J. 1999 Feb 15;338 ( Pt 1)(Pt 1):167-73.
Cardiac muscle expresses sarcoplasmic/endoplasmic-reticulum Ca2+ pump isoform SERCA2a; stomach smooth muscle expresses SERCA2b. In 2-day-old rabbits, cardiac muscle contained levels of SERCA2 protein that were 100-200-fold those in the stomach smooth muscle. In nuclear run-on assays, the rate of SERCA2 gene transcription in heart nuclei was not significantly higher than in the stomach smooth-muscle nuclei. However, the SERCA2 mRNA levels (mean+/-S.E.M.) were (29+/-4)-fold higher in the heart. In both tissues the SERCA2 mRNA was associated with polyribosomes. In a sucrose-density-gradient sedimentation velocity experiment on polyribosomes, there was no difference in the sedimentation pattern of SERCA2 mRNA between the two tissues, suggesting that the translation efficiency of SERCA2 RNA in the two tissues is quite similar. Thus the main difference in the control of SERCA2 expression in the two tissues is post-transcriptional and pretranslational.
心肌表达肌浆网/内质网Ca2+泵同工型SERCA2a；胃平滑肌表达SERCA2b。在2日龄兔中，心肌中SERCA2蛋白水平是胃平滑肌中的100 - 200倍。在核转录分析中，心脏细胞核中SERCA2基因转录速率并不显著高于胃平滑肌细胞核。然而，心脏中SERCA2 mRNA水平（平均值±标准误）高出（29±4）倍。在两种组织中，SERCA2 mRNA均与多核糖体相关。在多核糖体的蔗糖密度梯度沉降速度实验中，两种组织中SERCA2 mRNA的沉降模式没有差异，表明两种组织中SERCA2 RNA的翻译效率相当相似。因此，两种组织中SERCA2表达调控的主要差异在于转录后和翻译前阶段。
