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Transcriptional regulation of adipogenesis by KLF4.

ABSTRACT: While adipogenesis is known to be controlled by a complex network of transcription factors, less is known about the transcriptional cascade that initiates this process. We report here the characterization of Krüppel-like factor 4 (KLF4) as an essential early regulator of adipogenesis. Klf4 is expressed in 3T3-L1 cells within 30 min after exposure to a standard adipogenic cocktail of insulin, glucocorticoids, and IBMX. Knockdown of KLF4 inhibits adipogenesis and downregulates C/EBPbeta levels. KLF4 binds directly to the C/EBPbeta (Cebpb) promoter as shown by chromatin immunoprecipitation and gel shift assays and, together with Krox20, cooperatively transactivates a C/EBPbeta reporter. C/EBPbeta knockdown increases levels of KLF4 and Krox20, suggesting that C/EBPbeta normally suppresses Krox20 and KLF4 expression via a tightly controlled negative feedback loop. KLF4 is specifically induced in response to cAMP, which by itself can partially activate adipogenesis. These data suggest that KLF4 functions as an immediate early regulator of adipogenesis to induce C/EBPbeta.

SUBMITTER: Birsoy K

PROVIDER: S-EPMC2430156 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature

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Transcriptional regulation of adipogenesis by KLF4.

Birsoy Kivanç K Chen Zhu Z Friedman Jeffrey J

Cell metabolism 20080401 4

While adipogenesis is known to be controlled by a complex network of transcription factors, less is known about the transcriptional cascade that initiates this process. We report here the characterization of Krüppel-like factor 4 (KLF4) as an essential early regulator of adipogenesis. Klf4 is expressed in 3T3-L1 cells within 30 min after exposure to a standard adipogenic cocktail of insulin, glucocorticoids, and IBMX. Knockdown of KLF4 inhibits adipogenesis and downregulates C/EBPbeta levels. KL ...[more]

PMID: 18396140

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Project description:Human papillomaviruses (HPVs) are epithelial tropic viruses that link their productive life cycles to the differentiation of infected host keratinocytes. A subset of the over 200 HPV types, referred to as high-risk, are the causative agents of most anogenital malignancies. HPVs infect cells in the basal layer, but restrict viral genome amplification, late gene expression, and capsid assembly to highly differentiated cells that are active in the cell cycle. In this study, we demonstrate that HPV proteins regulate the expression and activities of a critical cellular transcription factor, KLF4, through post-transcriptional and post-translational mechanisms. Our studies show that KLF4 regulates differentiation as well as cell cycle progression, and binds to sequences in the upstream regulatory region (URR) to regulate viral transcription in cooperation with Blimp1. KLF4 levels are increased in HPV-positive cells through a post-transcriptional mechanism involving E7-mediated suppression of cellular miR-145, as well as at the post-translational level by E6-directed inhibition of its sumoylation and phosphorylation. The alterations in KLF4 levels and functions results in activation and suppression of a subset of KLF4 target genes, including TCHHL1, VIM, ACTN1, and POT1, that is distinct from that seen in normal keratinocytes. Knockdown of KLF4 with shRNAs in cells that maintain HPV episomes blocked genome amplification and abolished late gene expression upon differentiation. While KLF4 is indispensable for the proliferation and differentiation of normal keratinocytes, it is necessary only for differentiation-associated functions of HPV-positive keratinocytes. Increases in KLF4 levels alone do not appear to be sufficient to explain the effects on proliferation and differentiation of HPV-positive cells indicating that additional modifications are important. KLF4 has also been shown to be a critical regulator of lytic Epstein Barr virus (EBV) replication underscoring the importance of this cellular transcription factor in the life cycles of multiple human cancer viruses.

Dataset Information

Transcriptional regulation of adipogenesis by KLF4.

Publications

Transcriptional regulation of adipogenesis by KLF4.

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