‘Junk' DNA meets the p53 network

Mol Syst Biol. 4: 231 A major part of the genome of higher eukaryotes consists of non‐coding sequences. In former times, these sequences were called ‘junk‐DNA’ as no specific function could be attributed to them. More recent research has shown that small non‐coding RNAs are contained in these parts of the genome. These non‐coding RNAs have a fundamental role in gene regulation. Regulation of gene expression in eukaryotes is multifaceted and additional layers of complexity are constantly discovered. In a recent article published in Molecular Systems Biology , Varda Rotter et al describe a network that combines several of such regulatory layers by integrating the concerted actions of the transcription factors p53, E2F1, their respective targets and three clusters of microRNAs (Brosh et al , 2008). MicroRNAs (miRNAs) are a relatively recently identified means for gene regulation. They are small, endogenous non‐coding RNAs, between 19 and 25 nt in length. In some cases, miRNAs are organised in clusters and transcribed as polycistrons, which are cleaved in the nucleus into shorter precursor miRNAs. These precursor miRNAs are exported into the cytoplasm where they are further processed. Mature …