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New regulatory role of BCL-6 is identified in insulin signaling pathway

Posted by RockyMoutain on 19 May 2009 at 14:43 GMT

Computational and functional analysis of growth hormone-regulated genes identifies the transcriptional repressor Bcl6 as a participant in GH-regulated transcription.

Chen Y, Lin G, Huo JS, Barney D, Wang Z, Livshiz T, States DJ, Qin ZS, Schwartz J.

Bioinformatics Program, Program in Cellular and Molecular Biology, Departments of Molecular & Integrative Physiology, Human Genetics, and Biostatistics, University of Michigan, Ann Arbor, MI.

For insight into transcriptional mechanisms mediating physiological responses to Growth Hormone (GH), data mining was performed on a profile of GH-regulated genes induced or inhibited at different times in highly responsive 3T3-F442A adipocytes. Gene Set Enrichment Analysis (GSEA) indicated that GH-regulated genes are enriched in pathways including phosphoinositide (PI) and insulin signaling, and suggested that SOCS2 and PI3 Kinase regulatory subunit p85alpha (Pik3r1) are important targets. Model-based Chinese Restaurant Clustering (CRC) identified a group of genes highly regulated by GH at times consistent with its key physiological actions. This cluster included IGF-1, PI3K p85alpha, SOCS2 and CIS. It also contains the most strongly repressed gene in the profile, B-cell lymphoma 6 (Bcl6), a transcriptional repressor. Quantitative real-time PCR verified the strong decrease in Bcl6 mRNA following GH treatment, and induction of the other genes in the cluster. Transcriptional network analysis of the genes implicated Signal Transducer and Activator of Transcription (Stat) 5 as hub regulating the most responsive genes, Igf1, Socs2, Cish and Bcl6. Transcriptional activation analysis demonstrated that Bcl6 inhibits SOCS2-luciferase and blunts its stimulation by GH. Occupancy of endogenous Bcl6 on SOCS2 DNA decreased after GH treatment, while occupancy of Stat5 increased concomitantly. Thus, GH-mediated inhibition of Bcl6 expression may reverse the repression of SOCS2 and facilitate SOCS2 activation by GH. Together these analyses identify Bcl6 as a participant in GH-regulated gene expression, and suggest an interplay between the repressor Bcl6 and the activator Stat5 in regulating genes which contribute to GH responses.

No competing interests declared.