DNA damage stress induces the expression of Ribosomal Protein S27a gene in a p53-dependent manner

• RPS27a gene expression is induced in response to DNA damage.
• RPS27a gene is a transcriptional target of p53.
• Interference with RPS27a expression down-regulates p21Waf-1 expression.
• Pro-apoptotic markers are induced after RPS27a overexpression.

The small ribosomal protein RPS27a is known to play a role in the activation of cellular checkpoints via p53 which links ribosome biogenesis to cell cycle progression. Here, we show that RPS27a gene is a direct transcriptional target of p53 and is overexpressed in response to DNA damage. Elevated RPS27a level was associated with increased expression of p53 and its target p21Waf1 gene. The RPS27a activity was specifically inhibited in the presence of a dominant negative mutant of p53. Down-regulation of ectopically expressed RPS27a by RNA interference blocked the activation of p21waf1 in response to DNA damage. Thus, RPS27a appears to be a novel stress sensor in the cell which amplifies p53 response to arrest cell cycle.