The discovery of microRNAs (miRNAs), which are small regulatory RNAs, has revealed a new level of complexity in the regulation of gene expression.  My laboratory is studying a miRNA cluster, a single RNA molecule processed into six individual miRNAs. Several studies have confirmed that the expression of this cluster is deregulated in numerous human cancers. Moreover, overexpression of this cluster accelerates tumour development in a mouse model of lymphoma. Our objective is to understand the regulation of miRNAs from this cluster and to search for new miRNAs that are regulated during the cell cycle. Understanding the mechanisms by which an oncogenic miRNA cluster is regulated will help determine how it promotes tumorigenesis.  Furthermore, the identification of miRNAs implicated in cell cycle progression raises the possibility that they regulate the expression of factors involved in cellular proliferation.