Regulation of Krüppel-like Factor 6 Tumor Suppressor Activity by Acetylation

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Abstract
Krüppel-like factor 6 (KLF6) is a zinc finger transcription factor and tumor suppressor that is inactivated in a number of human cancers by mutation, allelic loss, and/or promoter methylation. A key mechanism of growth inhibition by wild-type KLF6 is through p53-independent up-regulation of p21WAF1/cip1 (CDKN1A), which is abrogated in several tumor-derived mutants. Here we show by chromatin immunoprecipitation that transactivation of p21WAF1/cip1 by KLF6 occurs through its direct recruitment to the p21WAF1/cip1 promoter and requires acetylation by histone acetyltransferase activity of either cyclic AMP–responsive element binding protein–binding protein or p300/CBP-associated factor. Direct lysine acetylation of KLF6 peptides can be shown by mass spectrometry. A single lysine-to-arginine point mutation (K209R) derived from prostate cancer reduces acetylation of KLF6 and abrogates its capacity to up-regulate endogenous p21WAF1/cip1 and reduce cell proliferation. These data indicate that acetylation may regulate KLF6 function, and its loss in some tumor-derived mutants could contribute to its failure to suppress growth in prostate cancer.