A cross-talk between DNA methylation and H3 lysine 9 dimethylation at the KvDMR1 region controls the induction of Cdkn1c in muscle cells

Abstract

The cdk inhibitor p57 kip2 , encoded by the Cdkn1c gene, plays a critical role in mammalian development and in the differentiation of several tissues. Cdkn1c protein levels are carefully regulated via imprinting and other epigenetic mechanisms affecting both the promoter and distant regulatory elements, which restrict its expression to particular developmental phases or specific cell types. Inappropriate activation of these regulatory mechanisms leads to Cdkn1c silencing, causing growth disorders and cancer. We have previously reported that, in skeletal muscle cells, induction of Cdkn1c expression requires the binding of the bHLH myogenic factor MyoD to a long-distance regulatory element within the imprinting control region KvDMR1. Interestingly, MyoD binding to KvDMR1 is prevented in myogenic cell types refractory to the induction of Cdkn1c. In the present work, we took advantage of this model system to investigate the epigenetic determinants of the differential interaction of MyoD with KvDMR1. We show that treatment with the DNA demethylating agent 5-azacytidine restores the binding of MyoD to KvDMR1 in cells unresponsive to Cdkn1c induction. This, in turn, promotes the release of a repressive chromatin loop between KvDMR1 and Cdkn1c promoter and, thus, the upregulation of the gene. Analysis of the chromatin status of Cdkn1c promoter and KvDMR1 in unresponsive compared to responsive cell types showed that their differential responsiveness to the MyoD-dependent induction of the gene does not involve just their methylation status but, rather, the differential H3 lysine 9 dimethylation at KvDMR1. Finally, we report that the same histone modification also marks the KvDMR1 region of human cancer cells in which Cdkn1c is silenced. On the basis of these results, we suggest that the epigenetic status of KvDMR1 represents a critical determinant of the cell type-restricted expression of Cdkn1c and, possibly, of its aberrant silencing in some pathological conditions.

Genetic and Epigenetic Control of CDKN1C Expression: Importance in Cell Commitment and Differentiation, Tissue Homeostasis and Human Diseases

“…As matter of fact, both DNMT1 [ 56 , 103 ], and DNMT3a [ 56 ] have been found associated with CDKN1C promoter. Consistently with the importance of DNA methylation not only in paternal allele imprinting but also in p57 Kip2 expression modulation in specific cellular and cell cycle phase contexts, treatment of many human tumor cell lines with demethylating agents such as 5-azacytidine and 5-aza-2′-deoxycytidine results generally in p57 Kip2 expression activation [ 102 , 104 ].…”

“…Complete biallelic hypermethylation occurs in human tumors and tumor cell lines [ 100 , 101 ], as well as in some undifferentiated tissues and cell types such as skeletal myoblasts. In this cell model, the activation of the transcription factor MyoD drives DNA demethylation on the maternal allele, therefore allowing the Myo- d -dependent expression of p57 Kip2 [ 102 ].…”

Expression of Imprinted Genes Kcnq1 and Cdkn1c During the Course of Differentiation from Mouse Embryonic Stem Cells into Islet-like Cells in vitro

“…It is reported that the Kcnq1 gene, expressed in various tissues of the body, has an important physiological role in regulating water and salt metabolism [12]. Kcnq1 and Cdkn1c are 2 adjacent imprinted genes that are expressed from the maternal [13]. Interestingly, there is a relationship between abnormal imprinting genes and growth and development of various diseases.…”

DNA Methylation Targeting: The DNMT/HMT Crosstalk Challenge

“…Among the HKMT family, G9a and G9a-like protein (GLP) are two HKMTs that catalyze H3K9me1 and H3K9me2, and with Suv39H1, Suv39H2, and SETDB1, complete the SET-containing SUV39 protein family responsible for H3K9 methylation, an epigenetic modification found to be dependent on DNA methylation in human cancer cells [74,75,76]. G9a and GLP apparently form a functional heteromeric complex with in vivo H3K9 methyltransferase activity [76,77,78,79].…”

“…Indeed, DNA methylation is lost in G9a or GLP -mutated cells. G9a and GLP can recruit DNMT3a and DNMT3b directly or indirectly through the chromodomain protein M-phase phosphoprotein 8 (MPP8), leading to de novo DNA methylation [75,85,86,87,88]. …”