Components of a Pathway Maintaining Histone Modification and Heterochromatin Protein 1 Binding at the Pericentric Heterochromatin in Mammalian Cells

Abstract

Heterochromatin is a higher order chromatin structure that is important for transcriptional silencing, chromosome segregation, and genome stability. The establishment and maintenance of heterochromatin is regulated not only by genetic elements but also by epigenetic elements that include histone tail modification (e.g. acetylation and methylation) and DNA methylation. Here we show that the p33ING1-Sin3-HDAC complex as well as DNA methyltransferase 1 (DNMT1) and DNMT1-associated protein 1 (DMAP1) are components of a pathway required for maintaining proper histone modification and heterochromatin protein 1 binding at the pericentric heterochromatin. p33ING1 and DMAP1 interact physically and co-localize to heterochromatin in the late S phase, and both are required for heterochromatin protein 1 binding to heterochromatin. Although the p33ING1-Sin3-HDAC and DMAP1-DNMT1 complexes are recruited independently to pericentric heterochromatin regions, they are both required for deacetylation of histones and methylation of histone H3 at lysine 9. These data support a cooperative model for histone deacetylation, methylation, and DNA methylation in maintaining pericentric heterochromatin structure throughout cell divisions.Heterochromatin is that portion of the genome that generally remains condensed throughout the cell cycle and replicates late in the S phase because of its unique, higher order chromatin structure. Heterochromatic DNA is predominantly present in the centromeric and telomeric regions of the chromosome that are composed of repetitive DNA sequence elements. In general, heterochromatic DNA sequences are heavily methylated on cytosine of the CpG dinucleotides. It is suggested that the chief DNA methyltransferase DNMT1 1 is important for the maintenance of DNA methylation in mammalian cells (1, 2). In addition to methylated DNA, histones are found to be hypoacetylated and hypermethylated at heterochromatin. These distinct covalent modifications are thought to be important for heterochromatin structure and function and are faithfully transmitted to daughter cells during cell division (3).Among the enzymes that modify histone tails, the histone methyltransferase Suv39h was found to be specifically required for maintaining pericentric heterochromatin structure and genome stability (4). Methylation of histone H3K9 creates binding sites for heterochromatin protein 1 (HP1) (5, 6), a marker of heterochromatin that is thought to reinforce the structure of heterochromatin. Loss of Suv39h leads to delocalization of HP1 from the pericentric heterochromatin (4). On the other hand, prolonged treatment of cells with trichostatin A, a general histone deacetylase (HDAC) inhibitor, also disrupts the normal localization pattern of HP1 (7), suggesting that the localization of HP1 to heterochromatin also requires histone deacetylase activity to maintain histone hypoacetylation at pericentric heterochromatin. It remains unknown, however, which of the many HDAC complexes in the cell is responsible for such an effect.DNMT1 may provide a...

Ing1 Mediates p53 Accumulation and Chromatin Modification in Response to Oncogenic Stress

“…Although the chromatin defects observed might reflect indirect effects of Ing1 depletion in the implementation of senescence, the solid evidence linking ING1 to chromatin regulation clearly supports the participation of Ing1 in chromatin changes as the most likely mechanism. Interestingly, it has been proposed previously that p33 ING1 could play a role in HP1 deposition during formation of nascent constitutive heterochromatin (39). One possible explanation for our observation is linked to the reported ability of p33 ING1 to modulate histone acetylation (7,9,39).…”

“…Interestingly, it has been proposed previously that p33 ING1 could play a role in HP1 deposition during formation of nascent constitutive heterochromatin (39). One possible explanation for our observation is linked to the reported ability of p33 ING1 to modulate histone acetylation (7,9,39). There is clear pharmacological and genetic evidence indicating that histone deacetylation is needed for the tethering of HP1 proteins to chromatin (40 -43).…”

Haploinsufficiency of the mSds3 chromatin regulator promotes chromosomal instability and cancer only upon complete neutralization of p53

“…Therefore, it is formally possible that mSin3 proteins could participate in the establishment of pericentric heterochromatin which required to maintain a euploid genome. Along these lines, it is notable that mSin3A can bind centromeric regions in human cells (Xin et al, 2004), implicating mSin3A in the pericentromeric heterochromatinization process. Thus, the lack of aneuploidy and accelerated tumorigenesis could relate to potential redundancy with the highly related mSin3B homologue which also interacts with mSds3 (Alland et al, 2002).…”

A functional link between the tumour suppressors ARF and p33ING1

“…ING proteins have been linked functionally to the p53 pathway at different levels, including the control of p53 protein stability, as transcriptional cofactors, or through post-translational modifications of p53 (Nagashima et al, 2001;Nourani et al, 2001;Gozani et al, 2003). ING proteins also participate in chromatin remodelling through their association with histone deacetylases and histone acetyltransferases (Nourani et al, 2001;Feng et al, 2002;Kuzmichev et al, 2002;Vieyra et al, 2002;Xin et al, 2004;Goeman et al, 2005). The most extensively studied member of the ING family is p33ING1, one of the products of the ING1 locus (also referred to as p33ING1b, or ING1b elsewhere; Feng et al, 2002).…”

“…More importantly, there is ample evidence, both in mammals and yeast, showing that ING proteins can form complexes with histone deacetylases and histone acetyltransferases. Based on this, it has been suggested that ING proteins could play a role in transcriptional control, through chromatin remodelling (Nourani et al, 2001;Skowyra et al, 2001;Feng et al, 2002;Kuzmichev et al, 2002;Vieyra et al, 2002;Xin et al, 2004;Goeman et al, 2005). An increasing number of evidences indicate that ARF can have a direct role in transcriptional control (Kamijo et al, 1998;Rocha et al, 2003Rocha et al, , 2005Calabro et al, 2004;D'Amico et al, 2004;Datta et al, 2004;Kalinichenko et al, 2004;Qi et al, 2004) and, therefore, it is feasible that ARF might cooperate with p33ING1 in transcriptional regulation, through chromatin remodelling processes.…”