FIG. 7.
Reexpression of Est1-D514A mutant protein switches the est1Δ-derived type II survivor to a type I survivor. (A) Telomere Southern blot analysis of type II survivors that express Est1-D514A mutant protein. est1Δ-derived type II survivors transformed with pRS315-EST1, pRS315-est1-D514A, or pRS315 plasmid were passaged on Leu− medium. Genomic DNA from the indicated restreaks (at the top) was digested by XhoI and subjected to Southern blot analysis using a TG1-3 probe. (B) Model of Est1's functions in telomere protection. In the presence of Est1, G tail could be converted into G quadruplex. The higher-order DNA structure on one hand avoids telomere being recognized by recombination factors and on the other hand activates telomerase.