Fitzgerald M S, McKnight T D, Shippen D E
Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843, USA.
Proc Natl Acad Sci U S A. 1996 Dec 10;93(25):14422-7. doi: 10.1073/pnas.93.25.14422.
Telomerase activity is developmentally regulated in mammals. Here we examine telomerase activity in plants, whose development differs in fundamental ways from that of animals. Using a modified version of the telomere repeat amplification protocol (TRAP) assay, we detected an activity in extracts from carrots, cauliflower, soybean, Arabidopsis, and rice with all the characteristics expected for a telomerase synthesizing the plant telomere repeat sequence TTTAGGG. The activity was dependent on RNA and protein components, required dGTP, dATP, and dTTP, but not dCTP, and generated products with a seven nucleotide periodicity. Telomerase activity was abundant in cauliflower meristematic tissue and undifferentiated cells from Arabidopsis, soybean, and carrot suspension cultures, but was low or not detectable in a sampling of differentiated tissues from mature plants. Telomerase from cauliflower meristematic tissues exhibited relaxed DNA sequence requirements, which might reflect the capacity to form telomeres on broken chromosomes in vivo. The dramatic differences in telomerase expression and their correlation with cellular proliferation capacity mirror changes in human telomerase levels during differentiation and immortalization. Hence, telomerase activation appears to be a conserved mechanism involved in conferring long-term proliferation capacity.
端粒酶活性在哺乳动物中受到发育调控。在此，我们研究植物中的端粒酶活性，植物的发育在基本方面与动物不同。使用改良版的端粒重复序列扩增协议（TRAP）检测法，我们在胡萝卜、花椰菜、大豆、拟南芥和水稻的提取物中检测到一种活性，其具有合成植物端粒重复序列TTTAGGG的端粒酶所预期的所有特征。该活性依赖于RNA和蛋白质成分，需要dGTP、dATP和dTTP，但不需要dCTP，并产生具有七个核苷酸周期性的产物。端粒酶活性在花椰菜分生组织以及拟南芥、大豆和胡萝卜悬浮培养物的未分化细胞中丰富，但在成熟植物的分化组织样本中较低或无法检测到。来自花椰菜分生组织的端粒酶对DNA序列要求较为宽松，这可能反映了其在体内断裂染色体上形成端粒的能力。端粒酶表达的显著差异及其与细胞增殖能力的相关性反映了人类端粒酶水平在分化和永生化过程中的变化。因此，端粒酶激活似乎是一种保守机制，参与赋予长期增殖能力。
