The Gut-enriched Krüppel-like Factor (Krüppel-like Factor 4) Mediates the Transactivating Effect of p53 on the p21 Promoter

Abstract

An important mechanism by which the tumor suppressor p53 maintains genomic stability is to induce cell cycle arrest through activation of the cyclin-dependent kinase inhibitor p21 WAF1/Cip1 gene. We show that the gene encoding the gut-enriched Krü ppel-like factor (GKLF, KLF4) is concurrently induced with p21 WAF1/Cip1during serum deprivation and DNA damage elicited by methyl methanesulfonate. The increases in expression of both Gklf and p21 WAF1/Cip1 due to DNA damage are dependent on p53. Moreover, during the first 30 min of methyl methanesulfonate treatment, the rise in Gklf mRNA level precedes that in p21, suggesting that GKLF may be involved in the induction of p21 Indeed, GKLF activates p21WAF1/Cip1 through a specific Sp1-like cis-element in the p21 WAF1/Cip1 proximal promoter. The same element is also required by p53 to activate the p21 WAF1/Cip1 promoter, although p53 does not bind to it. Potential mechanisms by which p53 activates the p21 WAF1/Cip1 promoter include a physical interaction between p53 and GKLF and the transcriptional induction of Gklf by p53. Consequently, the two transactivators cause a synergistic induction of the p21 WAF1/Cip1 promoter activity. The physiological relevance of GKLF in mediating p53-dependent induction of p21 WAF1/Cip1 is demonstrated by the ability of antisense Gklf oligonucleotides to block the production of p21 WAF1/Cip1 in response to p53 activation. These findings suggest that GKLF is an essential mediator of p53 in the transcriptional induction of p21 WAF1/Cip1 and may be part of a novel pathway by which cellular responses to stress are modulated.

Krüppel-like factors 4 and 5: the yin and yang regulators of cellular proliferation

“…DNA damage caused by methyl methanesulfonate (MMS) [16] or γ irradiation [17] leads to the induction of KLF4 expression in a p53-dependent manner. The increase in KLF4 mRNA level parallels the increase in the level of p21 WAF1/Cip1 mRNA, a major cyclin-dependent kinase inhibitor [16]. Importantly, KLF4 was shown to transactivate the p21 WAF1/Cip1 promoter by binding to a specific Sp1-like ciselement in the proximal p21 WAF1/Cip1 promoter.…”

“…This same element is also needed for p53 to activate p21 WAF1/Cip1 transcription, although p53 does not directly bind to it. Instead, p53 and KLF4 physically interact with each other, thus allowing p53 to gain access to the p21 WAF1/Cip1 promoter and activate p21 WAF1/Cip1 transcription [16]. A consequence of the p53-dependent activation of p21 WAF1/Cip1 expression following DNA damage is an arrest in the cell cycle at both the G 1 /S and G 2 /M transition points.…”

“…KLF4 then exerts a multitude of effects on expression of downstream genes by activating ( ) or inhibiting their expression ( ). References in support of the specific pathways are as follows: p53 KLF4 p21 [16]; KLF4 cyclin D/Cdk4 [19]; KLF4 cyclin B/Cdc2 [18]; KLF4 cyclin E/Cdk2 [21]; KLF4 STK15 [20]; KLF4 14-3-3 σ ; KLF4 BUB1/MAD2 [20].…”

KLF4, p21 and context-dependent opposing forces in cancer

“…13) and KLF7 (REF. 18)), KLF4 activates transcription of CDKN1A 23,24 . The functional status of p21 (also known as CIP1, WAF1, CAP20 or SDI1 ) seems to be intimately related to KLF4's function as either an anti-proliferative or, rather, a transforming gene.…”

Mutant p53 subverts p63 control over KLF4 expression in keratinocytes

“…Interestingly, maintaining elevated levels of KLF4 prevents apoptosis mediated by p53 (Ghaleb et al, 2007), and elimination of KLF4 induction leads to apoptosis in cells treated with nonapoptotic doses of DNA-damaging agents (Zhou et al, 2009). KLF4 activates CDKIs, p21, p27 and p57 (Chen et al, 2001Wei et al, 2006;Swamynathan et al, 2008); in particular, it cooperates with p53 in activating p21 (Zhang et al, 2000). KLF4 represses p53 transcription by binding to GC boxes in the p53 promoter: under these conditions, the levels of p21 and Cyclin D1 are crucial for deciding as to whether KLF4 exerts a tumor suppressive-high p21 or oncogenic-high Cyclin D1 activity (Rowland et al, 2005).…”