Computational and functional analysis of growth hormone (GH)-regulated genes identifies the transcriptional repressor B-cell lymphoma 6 (Bc16) as a participant in GH-regulated transcription.
For insight into transcriptional mechanisms mediating physiological responses to 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 indicated that GH-regulated genes are enriched in pathways including phosphoinositide and insulin signaling and suggested that suppressor of cytokine signaling 2 (SOCS2) and phosphoinositide 3' kinase regulatory subunit p85alpha (Pik3r1) are important targets. Model-based Chinese restaurant clustering identified a group of genes highly regulated by GH at times consistent with its key physiological actions. This cluster included IGF-I, phosphoinositide 3' kinase p85alpha, SOCS2, and cytokine-inducible SH2-containing protein. 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 after 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, whereas 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.
Chen
Yili
Y
Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-5622. jeschwar@umich.edu.
Lin
Grace
G
Huo
Jeffrey S
JS
Barney
Deborah
D
Wang
Zhenni
Z
Livshiz
Tamara
T
States
David J
DJ
Qin
Zhaohui S
ZS
Schwartz
Jessica
J
D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology / Q000379:methods*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000235:genetics*; D013006:Growth Hormone / Q000494:pharmacology*; D015151:Immunoblotting; D051379:Mice; D051560:Proto-Oncogene Proteins c-bcl-6; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000502:physiology; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics
C490010:Bcl6 protein, mouse; D004268:DNA-Binding Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D050799:STAT5 Transcription Factor; C491409:Socs2 protein, mouse; D050826:Suppressor of Cytokine Signaling Proteins; D013006:Growth Hormone