T. brucei activity monitored directly by telomerase primer-extension assay. Reactions were performed with DEAE fraction and primer tel 2. Lane 1, standard reaction; lane 2, extract pretreated with 100 ng of RNase A; lane 3, extract incubated with RNasin before addition of RNase A; lane 4, RNase A treatment after telomerase reaction (+); lane 5, nP, no input primer, lane 6, nE, extract substituted by reaction buffer; lane M, terminal deoxynucleotidyltransferase used to label tel 6 with [α-32P]dCTP (19 indicates the position of the primer plus 1-nt molecular weight marker).