Lung Krüppel-like Factor Contains an Autoinhibitory Domain That Regulates Its Transcriptional Activation by Binding WWP1, an E3 Ubiquitin Ligase

Abstract

Lung Krü ppel-like factor (LKLF/Krü ppel-like factor 2), a member of the Krü ppel-like factor family of transcription factors, is expressed predominately in the lungs, with low levels of expression in other organs such as heart, spleen, skeletal muscle, and testis. LKLF is essential during pulmonary development and singlepositive T-cell development and is indispensable during mouse embryogenesis. In this study, we performed a series of experiments to define the activation domain of LKLF as a means to further advance the understanding of the molecular mechanisms underlying transcriptional regulation by this transcription factor. Using deletion analysis, it is shown that LKLF contains a transcriptional activation domain as well as a strong autoinhibitory subdomain. The inhibitory subdomain is able to independently suppress transcriptional activation of other strong activators such as viral protein 16, VP16. This occurs either when the inhibitory domain is fused directly to VP16 or when the inhibitory domain is independently bound to DNA by GAL4 DNA-binding domain independent of the VP16 activator. Overexpression of the LKLF autoinhibitory domain alone potentiates transactivation by wild type LKLF, suggesting that the inhibitory domain binds a cofactor that prevents LKLF from transactivating. A yeast-two hybrid screen identified WWP1, an E3 ubiquitin ligase that binds specifically to the LKLF inhibitory domain but not to other transcription factors. In mammalian cells, WWP1 functions as a cofactor by binding LKLF and suppressing transactivation. These data demonstrate that LKLF contains multiple domains that either potentiate or inhibit the ability of this factor to function as an activator of transcription; moreover, regulation of LKLF transactivation is attenuated by an E3 ubiquitin ligase, WWP1.

FBW7 regulates endothelial functions by targeting KLF2 for ubiquitination and degradation

“…Although many studies have shown that KLF2 mRNA expression is regulated by various signals, including stress, growth factors and cytokines in endothelial cells, the mechanism that 815 npg regulates the KLF2 abundance at the posttranslational level has remained largely unknown [7]. A previous study showed that the E3 ubiquitin ligase WWP1 inhibits KLF2 transcriptional activity and targets KLF2 for ubiquitination and degradation in a ubiquitin ligase activityindependent manner [40,41]. A recent study showed E3 ubiquitin ligase Smurf1 targets KLF2 for degradation in H1299 cells [42].…”

The E3 Ubiquitin Ligase SMAD Ubiquitination Regulatory Factor 2 Negatively Regulates Krüppel-like Factor 5 Protein

“…Hence, the posttranslational regulation of KLF5 by E3 ubiquitin ligases appears to be highly complex and dynamic. For instance, besides SMURF2, KLF5 is degraded by a related ubiquitin ligase, WWP1 (5), that also targets KLF2 (28,29). WWP1 is a Nedd4 family of HECT ubiquitin ligases that recently included SMURFs (2).…”

Krüppel-like Factors: Three Fingers in Many Pies

“…Not surprisingly, in each case it can be whittled down to a minimal activation module (44 -47). However, a region adjacent to their zinc fingers behave functionally as inhibitory modules (45)(46)(47), implying that the roles of KLF1, -2, and -4 in transcriptional control is complex and may be sensitive to selective modification and protein interactions.…”