An Acetylation/Deacetylation-SUMOylation Switch through a Phylogenetically Conserved ψKXEP Motif in the Tumor Suppressor HIC1 Regulates Transcriptional Repression Activity

Abstract

Tumor suppressor HIC1 (hypermethylated in cancer 1) is a gene that is essential for mammalian development, epigenetically silenced in many human tumors, and involved in a complex pathway regulating P53 tumor suppression activity. HIC1 encodes a sequence-specific transcriptional repressor containing five Krüppel-like C 2 H 2 zinc fingers and an N-terminal BTB/POZ repression domain. Here, we show that endogenous HIC1 is SUMOylated in vivo on a phylogenetically conserved lysine, K314, located in the central region which is a second repression domain. K314R mutation does not influence HIC1 subnuclear localization but significantly reduces its transcriptional repression potential, as does the mutation of the other conserved residue in the KXE consensus, E316A, or the overexpression of the deSUMOylase SSP3/SENP2. Furthermore, HIC1 is acetylated in vitro by P300/CBP. Strikingly, the K314R mutant is less acetylated than wild-type HIC1, suggesting that this lysine is a target for both SUMOylation and acetylation. We further show that HIC1 transcriptional repression activity is positively controlled by two types of deacetylases, SIRT1 and HDAC4, which increase the deacetylation and SUMOylation, respectively, of K314. Knockdown of endogenous SIRT1 by the transfection of short interfering RNA causes a significant loss of HIC1 SUMOylation. Thus, this dualdeacetylase complex induces either a phosphorylation-dependent acetylation-SUMOylation switch through a KXEXXSP motif, as previously shown for MEF2, or a phosphorylation-independent switch through a KXEP motif, as shown here for HIC1, since P317A mutation severely impairs HIC1 acetylation. Finally, our results demonstrate that HIC1 is a target of the class III deacetylase SIRT1 and identify a new posttranslational modification step in the P53-HIC1-SIRT1 regulatory loop.

Sirtuins: critical regulators at the crossroads between cancer and aging

“…Similar to the intimate feedback loop with E2F1, SIRT1 interacts with HIC1 and represses its own expression . SIRT1 also deacetylates HIC1 and promotes HIC1 sumoylation at the same lysine acetylated by the histone acetyltransferases (HATs) CBP/p300 (Stankovic-Valentin et al, 2007). HIC1 functions as a transcriptional repressor when deacetylated and sumoylated (Stankovic-Valentin et al, 2007).…”

“…SIRT1 also deacetylates HIC1 and promotes HIC1 sumoylation at the same lysine acetylated by the histone acetyltransferases (HATs) CBP/p300 (Stankovic-Valentin et al, 2007). HIC1 functions as a transcriptional repressor when deacetylated and sumoylated (Stankovic-Valentin et al, 2007). HIC1 promoter hypermethylation occurs during tumorigenesis and aging, leading to the upregulation of SIRT1 (Chen et al, 2003.…”

Regulation of the sumoylation system in gene expression

“…In some cases, sumoylation actually acts as a recognition signal for a ubiquitin ligase [23]. The interplay between sumoylation and acetylation has been observed in the regulation of proteins such as MEF2, histone, and hypermethylated in cancer 1 (HIC1) [38][39][40][41]. In the case of MEF2, the sumoylation-acetylation switch is regulated by phosphorylation [39].…”

Loss of Hypermethylated in Cancer 1 (HIC1) in Breast Cancer Cells Contributes to Stress-induced Migration and Invasion through β-2 Adrenergic Receptor (ADRB2) Misregulation

“…D, quantitative real time PCR analyses and (E) immunoblot assays of HIC1 and of relevant target genes in WI-38 cells infected by pBABE-FLAG-HIC1 or by pBABE as control. ƒ, detection of SUMOylated forms of HIC1 (33). F and G, inactivation of endogenous HIC1 in WI-38 cells up-regulates ADRB2.…”