p44 Functions in Prostate Epithelial Cells Figure 1. P44 nuclear translocation is associated with functional differentiation of the prostate gland. (A) P44 nuclear translocation during prostate development. P44 immunostaining (in brown) in epithelial cells in the dorsal lateral prostates of mice at various ages. (B) Analysis of secretory proteins from prostate glands of mice at 17, 30, and 60 days old. Protein secretions were resolved on a 5–20% SDS-polyacrylamide gradient gel and the gel was stained with Coomassie Brilliant Blue R-250. An equal volume (5 ml of prostate secretions was loaded onto each lane. The migration of molecular weight markers is indicated in lane 1. (C) Quantitative RT-PCR analysis of mRNA expression of three prostate-secreted proteins. Total RNAs were isolated from whole prostate glands, and amounts of three (probasin, PSP94, and SBP) mRNAs were measured by real-time PCR. Relative expression indicates specific mRNA levels divided by b-actin mRNA levels. doi:10.1371/journal.pone.0049173.g001 the cell cycle at the G1/G0 phase transition [18,19]. Prostate epithelium that lacked p44 did not fully differentiate and was deficient in secretory protein production [17], indicating that nuclear p44 is required for differentiation and functionality of the prostate. More recently, we also found that p44 is essential and sufficient for proliferation of lung epithelial cells, and loss of p44 PLOS ONE | www.plosone.org 2 November 2012 | Volume 7 | Issue 11 | e49173