Cordycepin affects poly(A) tail length and cell proliferation at low concentrations. A, RNA ligation poly(A) tests on RNA from NIH3T3 cells treated with different doses of cordycepin. RNase H + Oligo(dT) indicates RNA from untreated cells digested with RNase H and oligo(dT) to remove the poly(A) tail as a control. The GenBank™ gene name abbreviations indicate which mRNAs were tested: Hif1a (hypoxia-inducible factor 1α), Cdkn1a (p21/Waf/Cip), Atf4 (activating transcription factor 4), Actg1 (gamma1 actin), Rps4X (X-linked ribosomal protein S4), and Rpl28 (ribosomal protein L28). B, Klenow priming poly(A) tests on a time course of cordycepin treatment. On the right side the panels shows the distribution of the intensity in each lane as a percentage of the maximum intensity in that lane on the vertical axis and the size of the poly(A) test products in base pairs on the horizontal axis. Black, oligo(dT) RNase A-treated sample; purple, no treatment; green, 15-min cordycepin; dark blue, 30-min cordycepin; light blue, 45-min cordycepin; and orange, 60-min cordycepin. C, Northern blot for Cdkn1a and β-actin (Act1b) on total RNA isolated from cells treated with 50 μm cordycepin for the indicated times. D, cell numbers after 72 h of treatment with cordycepin (medium refreshed daily, including drug).