Genome-wide analysis of YY2 versus YY1 target genes

Yin Yang 1 (YY1) is a critical transcription factor controlling cell proliferation, development and DNA damage responses. Although two homologous Drosophila YY family members (pleiohomeotic (pho)) and pleiohomeotic-like (phol)) are redundant, the functional significance of a recently described mammalian YY1-like gene (YY2) is unknown. Using microarray and gene set enrichment analysis (GSEA), we found that lentiviral constructs containing short hairpin loop YY1- and YY2-specific inhibitory RNAs (shYY1 and shYY2) caused significant changes in both redundant and distinguishable expression patterns. Ribosomal protein genes were the most significant gene set up-regulated by both shYY1 and shYY2, although combined shYY1/shYY2 knockdowns were not additive. In contrast, shYY2 reversed anti-proliferative effects of shYY1 on E2F target genes, and shYY2 particularly altered UV damage response, platelet-specific genes and mitochondrial function genes. The most YY2-specific gene was the platelet glycoprotein CD36 whose ligand is thrombospondin - a key UV response gene. We found that decreases in YY1 or YY2 caused inverse changes in UV sensitivity, and that their combined loss reversed their respective individual effects. Taken together, our studies show that YY2 is not redundant to YY1, and YY2 is a significant regulator of genes previously thought to uniquely respond to YY1. Functions of thrombospondin and CD36 in inflammation, atherogenesis, innate immunity and malaria pathogenesis reveal new potential regulatory roles for YY1 and YY2.

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Chen L, Shioda T, Coser KR, Lynch MC, Yang C, Schmidt EV