title: Mammalian microRNAs: a small world for fine-tuning gene expression.
abstract: The basis of eukaryotic complexity is an intricate genetic architecture where parallel systems are involved in tuning gene expression, via RNA-DNA, RNA-RNA, RNA-protein, and DNA-protein interactions. In higher organisms, about 97% of the transcriptional output is represented by noncoding RNA (ncRNA) encompassing not only rRNA, tRNA, introns, 5' and 3' untranslated regions, transposable elements, and intergenic regions, but also a large, rapidly emerging family named microRNAs. MicroRNAs are short 20-22-nucleotide RNA molecules that have been shown to regulate the expression of other genes in a variety of eukaryotic systems. MicroRNAs are formed from larger transcripts that fold to produce hairpin structures and serve as substrates for the cytoplasmic Dicer, a member of the RNase III enzyme family. A recent analysis of the genomic location of human microRNA genes suggested that 50% of microRNA genes are located in cancer-associated genomic regions or in fragile sites. This review focuses on the possible implications of microRNAs in post-transcriptional gene regulation in mammalian diseases, with particular focus on cancer. We argue that developing mouse models for deleted and/or overexpressed microRNAs will be of invaluable interest to decipher the regulatory networks where microRNAs are involved.
authors.affiliation: Department of Microbiology and Immunology, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, PA 19107, USA.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Sevignani
authors.forename: George A
authors.initials: GA
authors.lastname: Calin
authors.forename: Linda D
authors.initials: LD
authors.lastname: Siracusa
authors.forename: Carlo M
authors.initials: CM
authors.lastname: Croce
mesh_terms: D000818:Animals; D015870:Gene Expression; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*
chemical_list: D035683:MicroRNAs