Figure 4.

Depletion of ZONAB by RNA interference inhibits G1/S-phase transition. (A) Wild-type MDCK cells or cells stably expressing RNA duplexes corresponding to region I (ZONAB-RD-I c1 and c2) or II (ZONAB-RD-II c8 and c9) of ZONAB, or control RNA duplexes (control-RD c1 and c3) were grown for 2 d and then lysed and processed for electrophoresis. The samples were immunoblotted with anti-ZONAB and anti–α-tubulin antibodies. (B) Wild-type and transfected MDCK cells expressing the indicated RNA duplexes were plated at low confluence and synchronized in low serum. Cell cycle entry was triggered by serum addition, and progression to S-phase was monitored by determining the fraction of cell incorporation of BrdU. Shown are means ± 1 SD of at least two independent clones per type of RNA duplex that were analyzed in two independent experiments. Both ZONAB-directed RNA duplexes significantly inhibited entry into S-phase (t test; P < 0.02).