Identification of Structural Motif of RNAs Interacting with the G-rich Sequence RNA

摘要

Guanine-rich tracts are observed in the terminal segments of eukaryotic genomes. These guanine-rich sequences have the potential to form the non-carnonieal four-stranded topology called G-quadruplexes. The G-quadruplexes are built from the stacking of successive GGGG tetrads and stabilized by bound monovalent Na~+ and K~+ cations. The G-quadruplexes play a biological role in DNA telomere ends, the purine-rich DNA strands of the oncogenic promoter elements such as c-myc and c-kit, and RNA 5'-untranslated region (UTR) in close to translational start sites. Telomeres located at the ends of eukaryotic chromosomes are composed of the tandem DNA repeats of guanine-rich sequences and essential for chromosome stability. They appear to play a critical role in cellular aging and cancer. Telomeric DNA ends decrease in length after each round of cell division in somatic cells. But the telomere length can be maintained by the enzyme telomerase, a ribonucleoprotein complex with reverse transcriptase activity expressed in most cancer cells. So telomeres and telomerases correlated with cancer progression and have been used for the targets of anti-cancer agents.