Lung Kruppel-like factor contains an autoinhibitory domain that regulates its transcriptional activation by binding WWP1, an E3 ubiquitin ligase

Lung Kruppel-like factor (LKLF/Kruppel-like factor 2), a member of the Krup pel-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 de velopment and single-positive T-cell development and is indispensable durin g 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 u nderstanding of the molecular mechanisms underlying transcriptional regulat ion by this transcription factor. Using deletion analysis, it is shown that LKLF contains a transcriptional activation domain as well as a strong auto inhibitory subdomain. The inhibitory subdomain is able to independently sup press transcriptional activation of other strong activators such as viral p rotein 16, VP16. This occurs either when the inhibitory domain is fused dir ectly to VP16 or when the inhibitory domain is independently bound to DNA b y GAL4 DNA-binding domain independent of the VP16 activator. Overexpression of the LKLF autoinhibitory domain alone potentiates transactivation by wil d type LKLF, suggesting that the inhibitory domain binds a cofactor that pr events LKLF from transactivating. A yeast-two hybrid screen identified WWP1 , an E3 ubiquitin ligase that binds specifically to the LKLF inhibitory dom ain but not to other transcription factors. In mammalian cells, WWP1 functi ons as a cofactor by binding LKLF and suppressing transactivation. These da ta demonstrate that LKLF contains multiple domains that either potentiate o r inhibit the ability of this factor to function as an activator of transcr iption; moreover, regulation of LKLF transactivation is attenuated by an E3 ubiquitin ligase, WWP1.